Ok Admin-kun, this has gone on long enough. First make a hidden field on the post form, which when checked to see if it is filled out, will autoban the user. Bots fill in all the fields that they can. Second, if that doesn't work create an image captcha as described at https://en.m.wikibooks.org/wiki/CAPTCHA/Integration/Images_and_PHP for only new threads which I believe may be a necessary step. Autoban all op posts containing ((that link)), in fact, you should block op posters from posting who only send an image and link.
I sure hope he implements it. This should really be SOP for all admins.