I use XChat (2.8.6). It runs 24/7. I think whenever my internet connection is reset (at least every 24 hours), my nickname gets an underscore (_) appended:
My nick john becomes john_, then it becomes john__, then john___ … and so on.
When I click left to the chat text field on my nickname, I can enter a new name. At the moment, I re-enter "john" there everytime and for each server. Which is annoying. Is there a way to change my nickname globally (= for all servers) back to the registered "normal" form (without underscores) automatically?