I've noticed this trend go on for a while now. For most, if not all registered users, in the blog's commenting section, it says something along the lines of:
"This blog has not been commented on in over 30 days. There is no need to comment"
And the comments are locked with that message. However, unregistered users are apparently unrestrained from this, and have been bumping blogs that are over two years old for the past several months.
Does someone know why this is happening, and if we should stop it?