The highlighting of comments is the Scintilla lexer, which highlights several similar versions of properties files and is hard coded to use `#`, `!` and `;` for comments. There is not way to change that without changing Scintilla, which is a separate project from Geany, you can raise a request [here](https://sourceforge.net/p/scintilla/feature-requests/). But since all such properties files tend to use the extensions `.ini`, `.conf` etc interchangably its hard to tell them apart and I suggest it should remain general despite the fact that an occasional error may occur in highlighting.

The symbol parser is hard coded to use `#` and `//` as comments. There is no way of changing that without changing the ctags parser. The parsers mostly come from the [universal-ctags](https://github.com/universal-ctags/ctags/) project. The Geany one is the parent of the [uctags](https://github.com/universal-ctags/ctags/blob/master/parsers/iniconf.c) one, but that has been changed to look for `;` as well. There is an ongoing exercise to align Geany's parsers with uctags. @techee, maybe this should be added to the TODO list if it isn't already.

Seems to be fixed with the updated parser.