Thanks, I've deleted those collections.

Thanks for the heads up about this.  I didn't even realize there wasn't a report spam button there.  The issue is fixed now.

That tripped me up too, for about three seconds. Then I went ahead and reported the spamming user directly (there was just one). But a dedicated report spam button on collections doesn't hurt either.

Just a note to admins:

If you see a user spamming, you can go to their user account and click the delete account button, then select the option to delete the account and all of its content.

As a warning, please be very careful when doing this.  Occasionally comments look kind of spammy but aren't actually spam if you check into them.