Firstly, on TABCOMP should trigger even if native mIRC is unable to come up with a match. Currently, unless mIRC finds a match, on tabcomp does not trigger thus not allowing scripts to include there own handling.
I remember using scripts that used tabcompletition with arbitrary editbox text.
Added on TABCOMP event, triggers when a user presses the TAB key in an editbox and mIRC is about to perform tab completion. Halting the event prevents mIRC's default tab completion.
Was this really changed?