A little suggestion here. Wouldn't it be possible to suggest usernames when typing in private threads?
Right now users have to guess that they have typed in the right username.
Absolutely. I have dozens of such small things that I would love to add, but I'm currently delaying because its another work at current frontend that I will have to then do again in few months when I will be doing new frontend. It may be delayed until then, or it may happen in meantime during one of maintenance releases.