I’m not sure if this is a bug exactly, but I’ve noticed that the “usable by me” check doesn’t seem to work for styles. For collections, it weeds out collection pieces that I already have, but for styles, I still get all the “already collected” styles. I’m assuming that this is unintended. I’d really like to just search for styles that I don’t already have.
Unless the feature has become bugged, it also sorts out role-specific gear that you cannot equip. Not that any role-specific gear is worth anything on the broker, but it is an included function of the checkbox.
I get the feature/bug debate, but are we sure this is intentional? If it's not, then it should be considered a bug.
So a bug is when something is broken or otherwise behaving in a way that is not intended. In my experience the "Usable by me" feature has been working as you described for the past 12 years. How you think it should be working has been suggested before in the past. To my knowledge the feature has never been declared broken.