Marc Hoyois’s last comment to my question $$2$$-fiber product is a scheme then map of stacks is representable did not get notified in my inbox.

On top right of the page, there is an icon after my account picture. I get notifications if I click that. I get some times and I don’t get some times.

You can find all details about using notifications in comments in the network-wide FAQ: How do comment @replies work? (This link can be found also in comment-notifications tag-info.)

Notice that author of the post is always notified when there is a new comment. But since you're talking about an answer to your question posted by another user, you do not get automatically the notifications about all comments. So if somebody comments under that answer (or more generally under some other users' post), if you also posted a comment there, they can notify you by using the @username syntax.

There is one exception when this is actually not needed, I will quote from the linked FAQ post:

Note that if a user comments on their own post and there is only one other person who has previously commented on that post, then that person is also notified, even if @name is not used.

So as long as you and the post author (in this case the answerer) are the only users who posted comments there, you should get a notification. (However, this is not the case for the answer in the linked question.)

Looking at the comments which are displayed at the moment under the answer in question: The first comment by the answerer explicitly used "@PraphullaKoushik" - so you should be notified of that one. Neither the most recent comment by the answerer nor comments by the other user who was in that comment exchange use "@username" to notify you - so unless I missed something in the post explaining how comment replies work, there should be no notification about them in your inbox. (As already mentioned, the author of the post is notified.)

Some related posts:

• You are correct that I am asking about comment to Marc's answer.. – Praphulla Koushik Dec 4 at 12:25
• @PraphullaKoushik Thanks for editing the question to clarify this. (This makes my comment on your meta question - which asked exactly about this clarification - obsolete, so I have deleted it.) – Martin Sleziak Dec 4 at 12:30
• I now understand how it works.. Thank you. I personally feel I should get notified... As you mentioned how it works, I can be careful next time that I do not check just the inbox but actual post where I am expecting some comments.. Your answer is useful.. – Praphulla Koushik Dec 4 at 12:32
• My preference would be to get notifications for comments on answers to questions of mine. -- I mean, a comment may even point out that the answer is wrong -- and certainly I would want to know about this in that case. – Stefan Kohl Dec 4 at 13:06
• @StefanKohl Well, there are two feature requests in my posts which you can upvote to express that preference. (And maybe there are many other similar posts which I did not find.) And of course if you have enough time to do that, you can search a bit on Stack Apps to see whether some extensions available there accomplish this. – Martin Sleziak Dec 4 at 13:15
• @StefanKohl "My preference would be to get notifications for comments on answers to questions of mine." I mean exactly this.. – Praphulla Koushik Dec 4 at 13:17