I'd suggest that, while this doesn't necessarily relate to the ending as such, this might be useful to post and discuss in https://forums.larian.com/ubbthreads.php?ubb=showflat&Number=884832 rather than having too many different threads discussing Karlach's fate, which could dilute the feedback.

"You may call it 'nonsense' if you like, but I've heard nonsense, compared with which that would be as sensible as a dictionary!"