By default, Snarl stores all the notifications that were generated while I am away from the computer (say I locked the computer). When I come back to the computer it displays a notification indicating how many notifications I missed while I was away and invites me to see them. Actually, I do not care about any notifications I miss while I am away from the computer, so it would be nice to just ignore or discard these missed notifications.
To always discard notifications while I am away, open Settings → Presence → Away. The default setting for When Away is Log as Missed. Change it to Discard and you will no longer be bugged about missed notifications.
Tried with: Snarl R2.5