Threads The postbit should be a little wider by default.
 

I would assume the length of the postbit (in pixels* fixed/fluid) can be easily changed* but I think* by default* it should be a little wider... Maybe up to 10 px in additional width. Not only would it solve a lot of issues related to long user names* but it would also keep the content of each post from looking too wide* which can happen on higher resolutions.