on ^*:INVITE:#one,#two:{ join # | haltdef }
The channel being joined to opens minimized, as if join -n had been used, join -i doesn't work within the context of the INVITE event at all, and the event beep still gets triggered as reported in
this thread over a year ago. Auto-join is disabled. I have tested this on a clean unpatched mIRC v6.17 install.