Lighthouse by Active Reload is nice issue tracking application. Most apps in this category are extremely bloated [cough] Bugzilla [cough] or way too complicated and a nightmare to use [cough] Bugzilla [cough], but Lighthouse seems to find a nice balance between features and ease of use.

With that said, I recently spent an embarrassingly long amount of time trying to figure out how to assign an issue to someone else. There are a handful of UI controls on the screen while editing an issue, including this:

I see that I’m the responsible party, but there is no dropdown for choosing someone else. When I mouse over the block with my name in it, I see that the background color changes.

This is a subtle visual cue, but I figured out that I could click in this area and a new selection panel is rendered with other names in it.

Strictly speaking, there are no affordances with this design - that is there are no visual cues telling you that by interacting with this control, you will be able to select a different assignee. A simple inverted triangle would be a helpful cue:

Taking it a step further, a small overlay label when mousing over would make the interaction even more obvious:

Small things like this can really make a difference to your application’s usability.