Since comments gained the ability of some very limited formatting that's also a source of frustration involved. The syntax is, while similar to the main post syntax, still different enough that you stumble over the discrepancies every now and then.
*foo*-bar works in normal posts but not in comments.
Case in point here: How the hell does the parser work?
Or rather: What do I need to do to the string to work? Adding a space after the interior
* does work. But that's sort of a non-solution. Adding U+200B in there does not work (would have been too easy, I presume).
ETA: Ok, in the comments I've been doing some testing. It appears that everything that's a space seems to work (suggests
\s is used somewhere). Since the zero-width space isn't a space it doesn't work. While I used
foo-bar as a test string I also sometimes wanted to emphasize part of a non-hyphenated word, something like
*un*foo (which works in Markdown, even though it doesn't appear to work in the JS preview. However, I would have expected the hyphen-minus at least to count as a delimiter. Looks like the hair space is the best option so far.