System locale with the bots is set to En_us.utf8 so that shouldnt be of the issue, only the cyrillic letters will always get broken. ie.
[1:46am] <@XXX> зомбита

[1:46am] <@XXX> (XXX@XXX) 7><18B0

Edit: CP1251 works, only UTF-8 is not working, but it doesnt help since people are using mixed combo of cp1251 and/or utf-8
Final edit: That hacky utf-8 patch seemed to cure it, now the bot displays utf-8 and cp1251 properly. At least on channel text. (the one with editing main.c and tcl.c). That is good enough for me, since not using utf-8 encoded channel names.