Michal (or anyone else), could you please upload your log file? On Windows you may need to enable Hidden Items in File Explorer. Or, press the Windows key and R key at the same time, type in appdata and then hit enter.
We fixed some causes of chat problems in 0.7.7f and the chat was fine for us after several hours of testing. Your log file should help us find remaining issues.
I do realize it’s frustrating, but we do need information to solve the problem if it isn’t happening internally.
Neither of you are chat banned. There should be a message in the chat window stating so if you are.