Thanks for your bug report. I was able to reproduce this issue on the simosnap server.
Newer versions of mIRC use MONITOR instead of WATCH when a server supports both because MONITOR is the newer, and better, implementation, in the same way that WATCH is used over ISON when available.
mIRC expects hostnames to be sent in WATCH and MONITOR replies. For some reason, the simosnap server is sending user hostnames in WATCH replies - but not in MONITOR replies.
Technically, user hostnames are not required in MONITOR replies but I have never come across a case where a server has not sent this, since the usefulness of user hostnames is one of the reasons why these notify protocols were created over the older ISON protocol. So this is an odd MONITOR configuration choice by the simosnap server administrator.
In any case, I will make a change to allow MONITOR to work without user hostnames. This change should be in the next beta version.
