I didn't even know we were racing! Woohoo!
Drat! I'll get you back one day green man.
I guess the check if it's already posted button doesn't cover archives. Surely, you use that button.
I suggested the feature and thank you to @AOU for adding it. Yeah, I use it all of the time but like you said, it is not checking archive links.
I do try to go see what is in "new" before posting but I tend to post in batches while I am reading things and taking a break from work. I don't always notice if something has already been posted using archive/non-archive.
Since archive.x using a captcha to access the archived link, which prevents from grabbing a title and generate a thumbnail, there's no way to check if the source of an archived link has been already posted.
Yeah, I assumed it would not be possible without having an active crawler attempt to read the archive and match the title. Seems like a waste of time and resources.