Sorry, no, I don't acknowledge this as more common. You're using workarounds to make things work when they should not-- ie. a /timer to make $input work even though mIRC does not allow modal dialogs in events (for a very good reason). Let these scripts break.
You can make a 'PM / Query Blocker' script without using $input.
You can check (hash table, text file, access level, variables) and depending on result: close query, ignore nick, send message.Not common?