slight change to site: comments

We’ve been getting spammed. So I am now requiring comment submitters to have a previously allowed comment to be able to comment without issue.
I hate doing this, but I don’t want this to become yet another waste of bits, lousy with comment spam. If this doesn’t work, I’ll change it to require user login to comment.
[update] Since making the change, no spam has made it through, though they have tried. I just added some additional mechanisms to make it somewhat harder for the spammers. It will keep getting harder and harder for them, with very little effort (actually reduced effort) on my part. Scales well for me.