This bug report did not originally mention the platform and the renderer. I originally put them at the end, but it occurs to me that they're more useful up front. Thanks to @DavidRoberts and @GeraldEdgar for reminding me.
This is in Safari 16.3 on macOS 13.2, using any renderer. The behaviour I am describing seems to be very much a Heisenbug; the more I test it, the more erratically it behaves. Refreshing a page repeatedly, without changing anything else, will often cause the bug to appear and disappear. Sometimes the number will show while the page is loading, but then disappear while the load is complete. The preview while editing is also often different from the rendered result.
1. $$1 + 1 = 2.$$
produces
- $$1 + 1 = 2.$$
For me, that usually looks like this:
Notice that the number was swallowed. I would have expected it to behave like
1.
$$1 + 1 = 2.$$
$$1 + 1 = 2.$$
(For me, the latter always shows the number and the displayed equation on separate lines, which is what I think most TeX users would expect. As @DavidRoberts mentions, this different behaviour does not occur on Firefox. As I and @AsafKaragila mentioned, Chrome seems to behave differently, putting the first equation on the same line as the number. I think a TeX user would not expect this, but it is not an unreasonable implementation, so I do not complain.)
1.
but no line break; the second shows1.
and a line break. $\endgroup$