Sorry, I didn't read this, so probably I'm late. This patch only changes the text of received (incoming) messages, it doesn't change sent (outgoing) messages (I didn't need it). I think you are receiving the error because the server only allows UTF-8 text for messages you send. About repos: different people at different times contributed to some degree to BitchX, I think the most complete codebase is here in sourceforge but some in github diverged more recently, it's a bit confusing.
PATCH updated to work with recent version from git
PATCH updated to work with recent version from git
PATCH updated to work with recent version from git
PATCH updated to work with recent version of git
gmake missing .config.h