I think it would be useful if we could prevent mIRC from triggering events sent when ZNC plays back the message buffer, to prevent scripts from responding to commands or messages that may have been sent long ago.
I would suggest either somewhere in options being able to specify the maximum age in seconds for a timestamped message to trigger an event, or adding a new prefix to events to ignore messages sent with the @time prefix.
Rather crude example, but what about something like this?
on *:text:!foobar *:#:{ ; Buffer, dont execute if ($msgstamp) { echo $chan $timestamp Nope! | return } ; Not in buffer, do stuff if (!$msgstamp) { msg $chan do_stuff } }