1. Go to any document in the editor
2. Press the history button on a target translation
3. Enter a comment in the box and press 'Add comment'
4. Click the search filter and select translation-comment from the list
5. Enter the text of the comment into the search filter
6. Press Enter
The textflow that was commented on should be visible
Looks like it might be related to the refactoring changes for ZNTA-2297.
In fact this feature is searching for what Gettext calls a "translator comment", which Zanata can store but can't currently show or edit. Completely separate from review comments.
If it ever did show you a match, you wouldn't be able to see the matching comment. (Not until we add translator comment support.)
As it is, it's just confusing, so I'm going to remove it from the search auto-complete for now. The feature itself will still be there, just hidden. We can bring it back when it makes sense.