It seems to be a “smart quotes” problem. Stupid quotes (made of straight lines) work fine.
Seems an auto find/replace code would fix it. Although, smart quotes are just another ASCII character, so something’s swapping the proper ASCII interpretation for garbage.
It’s a character encoding issue.
The comment box page is marked as accepting UTF-8, but somewhere the UTF-8 is being parsed as windows-1252 or 8859/1, which is incorrect. It may also be the table in the database having a non-UTF8 character encoding.
source: I have lived through this hell myself.