Since each addon on OHM has a comment thread here on the forum it allows you to post everything from comments to bugs or anything to do with that particular addon. Making use of the forum also allows users to include attachments, code, etc. in their comments. Each addon on OHM has a link to it's thread here on the forum titled 'User Comments'.
There is also the Addon Support & Bugs forum which could be used as another way to report bugs for any addon.