I'm new to this GreaseMonkey thing, but there seems to be a few bugs here:

• the @includes at the beginning of the script should have a / (slash) at the end of the url (this is what I see on the URL when I hover my mouse on the Submitted links)
• it does not work at the moment for me (I'll debug it later to see what should happen)

Thanks for the extension!

Edit: I found the solution!

• replace the two "submitted" by "submitted/" (add a slash) in the two @include lines
• and change the document.evaluate from @class='titlerow' to @class='title'

Edit 2:

• it does not work if you click "Next" in the page of submitted comments, I mean, the second page won't have any downvotes at all.
• some spammers are writing their crap in the "comments" section, maybe it would be a good thing to allow the extension to downvote comments in the "comments/" URL too?

it does not work if you click "Next" in the page of submitted comments, I mean, the second page won't have any downvotes at all.

Change "submitted" in the include lines to "submitted/*".