Yeah, happens to all of us, don't feel bad :-)

Some submissions get unnoticed and some others with the exact same link gain traction and start having comments and being upvoted.

I'm sure if @Dang had spare time there would be a filter, during submission of a new link, to check whether the exact same link already exists.

> I'm sure if @Dang had spare time there would be a filter, during submission of a new link, to check whether the exact same link already exists.

There is. Duplicate submissions get redirected to the existing thread. Sometimes it doesn't kick in, for reasons obscure.