Further information. The strange sign Â(capital A with circumflex)) is not present when channel is unencrypted, so i guess that makes it a Fish problem, maybe? Changing font to a Unicode compliant one does not help, as stated in earlier post.
Regarding the encrypted topic problem, it seems like i can read encrypted topics set by myself, but not if it is set by others. They are using (as far as i know) mIRC 6.35 with old Fish.