# Disappearing "Hi!"

Just curious ...

A brand new member posted a question this afternoon, and I posted an answer.

I know him quite well, and he was here in Bristol to give a seminar two days ago, and without giving it much thought I began my answer with "Hi!".

The "Hi!" has disappeared.

Is this something the system does automatically? Or did some evil, but very on-the-ball, moderator surreptitiously remove it?

I'm not in the slightest offended or bothered, just curious ...

I began this answer with a salutation, and hopefully it was never posted, because that's what the system is supposed to do, as per Jeff Atwood's answer on Meta Stack Exchange:

We now automatically remove salutations from posts as they are entered.

I got really tired of performing this edit over and over, so anything matching the form of …

^                 # begins at start of body
\s*               # possible spaces
(
hii?(?![a-z])|    # any of these greeting words
hello|
h(e|a)y(?![a-z])|
dear|
greetings|
hai|
guys|
howdy|
h(i|e)ya|
hola
)
.*?               # followed by anything, up to...
(
[.,;!-]+          # one or more bits of punctuation
\s*               # possible spaces
|
(\r?\n)+          # one or more newlines
)


… is removed automagically at the time of submission to the server.

(The regex above is not currently accurate. After the discovery of automatic hair removal the regex has been altered, though I don't know the details. If at some time the new regex becomes public — and I remember to — I'll update that part of this answer.)

• The salutation ("Greetings,") was dutifully removed automatically. Nov 6 '15 at 18:13
• Thanks! Guess I'll have to stick with my usual "Yo, dude!" Nov 6 '15 at 18:26
• @Jeremy: Seems to me that "Ahoy!" should work as well. Especially if you post your question on Talk Like A Pirate Day.
– Asaf Karagila Mod
Nov 7 '15 at 9:58
• Holla! According to the no-hair-theorem there should be no hairs anyway, however if the SE network wide implementation of automatically removing friendly things such as hi, thanks, etc is really a good idea, is less clear... Nov 7 '15 at 14:46
• Here is an exercise. Construct an answer where this automatic script removes something important for the answer. Nov 7 '15 at 17:20
• @GeraldEdgar "Hairer proved in ..." Nov 7 '15 at 18:20
• @Dilaton this answer on meta Mathematics makes a pretty good case for removal, I think. Then I never heard a convincing argument for greetings in posts as there is not even a conversation that is started. Moreover, mostly they are so informal or even sloppy as to be borderline disrespectful.
– user9072
Nov 7 '15 at 19:30
• @Quid I know that on other sites, SE tries to systematically erase any traces that the content is written by living human communities instead of some non-social life forms. The (completely legitimate) goal of the company is to get steril libraries of Q&A, useful to an as large as possible amount of external Googlers, written by volunteers. However, in human academic online communities, treating each other with due respect and appreciation does never hurt. Nov 7 '15 at 20:11
• @Dilaton as I tried to explain I do not even find the greetings one usually sees to be respectful, often quite the contrary. Furthermore, I would not know that research papers, book reviews (or even opinion pieces) or most any other form of academic text starts with greeting the readership in general terms. (Obviously, a letter or an email does, but this is something quite different. Although, for the latter it actually starts to disappear even there.)
– user9072
Nov 7 '15 at 20:33
• I wonder whether we could have some statistics on how often the removal regex is triggered on MO (preferrably in posts that do not get closed anyway). Nov 9 '15 at 11:44
• @EmilJeřábek this would be interesting to know. In the interim to get a rough idea one can use searches for "Hello" and "Hi" and "Dear" like mathoverflow.net/search?tab=newest&q=hello or mathoverflow.net/search?tab=newest&q=hi or mathoverflow.net/search?tab=newest&q=dear with more than three thousand combined hits. Only a handful from after June 2013 when the script was introduced. I suspect the number to be significant, and one should also factor in a learning effect. That is, when the script deletes once the user might get the hint and not include the it next time.
– user9072
Nov 9 '15 at 12:05
• As I said, my original question was purely motivated by curiosity, and I certainly didn't intend to (re?)open a can of worms. I don't think that the danger of accidentally censoring the names of Hairer or Hi is a serious problem: I imagine most of us look at our posts after posting them, and would just be amused and find a workaround. On the other hand, I'm not entirely convinced of the need to remove salutations. In questions, it seems weird to start with "Hey guys!" or whatever. But we're a community where there's a fair chance that somebody answering a question by a brand-new member will .. Nov 9 '15 at 14:46
• ... know them from outside MO (as in my case), and in that case it just seemed to me that it would be friendly to express my pleasure that he had come to MO, and that making him welcome might marginally increase the chance that he'd stick around. Nov 9 '15 at 14:49
• @JeremyRickard The comments make some good points. On the last point: in my opinion a comment on the post is a good way to welcome somebody to the site. Generally, more conversational parts are in my opinion often better included in comments. On the need: well we still have about ten questions that start with "Hey guys" and hundreds that start with a spurious "Hi", "Hi all" etc. almost all from before we had that script.
– user9072
Nov 9 '15 at 15:02

Boundary regularity of suitable weak solution for the Navier-Stokes equations, J. Funct. Anal. 268 (2015), no. 8, 2171–2187, MR3318646.

The above is supposed to be a reference to a paper by the mathematician Hi Jun Choe. If it appears as a paper by Jun Choe, then the salutation-deletion software has been over-active.

Edit: worse than I thought; it deleted the whole of the name, not just the "Hi".

• The point being, this is not just a hypothetical discussion – there actually is a mathematician named Hi. Nov 9 '15 at 2:25
• "this is not just a hypothetical discussion" To me it seems, so far it is. Or would you know of an actual instance where this caused some problem? Hypothetical instances where the script could cause some problem got discussed at length elsewhere. For example, "Hello World" or some such thing, could somewhat plausibly be the start of some programming question. And so on. And so on.
– user9072
Nov 9 '15 at 7:36
• By the way, the actual problem here is that you do not correctly mark-up a copy-paste quote from MathSciNet : -)
– user9072
Nov 9 '15 at 7:49

${}$ Hi Jeremy,

The trick is to use tex. I preceded the salutation by dollar sign - open curly bracket - close curly bracket - dollar sign.

• Actually, MathJax/LaTeX is overkill here. Since the salutation must be at the very beginning of the post, I'm nearly certain that a zero-width space (Unicode U+200B or HTML &#8203;) would have the same effect, without having to render any MathJax. (Of course, it's more difficult to input such a character, but here's one for you to copy and paste: ​). Nov 8 '15 at 6:18
• If I see something like this on the man site I will edit it.
– user9072
Nov 8 '15 at 13:33

Hairer proved in his thesis that all frobbits are easily zapped.

A test of deletion.

in his thesis, proved that all frobbits are easily zapped.

Another test.

• Looks like you need some punctuation immediately after the offending salutation. Nov 7 '15 at 18:55

# Would you buy me a beer to teach you how to write "Hi!" (if you wish in large font) and the like without MathJax?

Doubt this can be prevented only with regexp...

• My linear algebra professor used to tell us that if we go to the matrix market, and someone offers us a matrix tat he worked on for a very long time, we should ask to pass only finitely many vectors through before buying. Then we should input the basis vectors, and we'll know the matrix without paying. In this case, just click edit. :-)
– Asaf Karagila Mod
Nov 13 '15 at 18:52
• @Asaf this needs 2000+ though. (One could read the source of the page.)
– user9072
Nov 13 '15 at 19:06
• @quid: Odd, I was sure that when I clicked the "edit" button (also in the link at the end of my comment) I could see exactly what was going on...
– Asaf Karagila Mod
Nov 13 '15 at 19:07
• @Asaf I am not sure what is odd as you have well over 2000 points.
– user9072
Nov 13 '15 at 19:08
• @quid: If only we could have had a feature for suggesting edits for people with <2000 points... :-)
– Asaf Karagila Mod
Nov 13 '15 at 19:11
• @Asaf indeed, this would be convenient for them in such a situation. As it works quite well on the main site, they might also implement it for the meta site, eventually.
– user9072
Nov 13 '15 at 19:17
• @quid: Huh, that's something I didn't know about the meta sites. Kudos!
– Asaf Karagila Mod
Nov 13 '15 at 19:23