Forum Moderators: phranque
A google search brings up a lot of results for that text, undoubtedly bots. Prevent them from registering in the first place and it won't be an issue. It appears most of the majority of the forums that text appears on are phpbb forums, there is very long thread on phpbb's site with numeraous mods for preventing bot registration, the mod that asks a question is bullet proof from my experience.
As far as why... I have theory about many of these posts that you see that at first glance normally wouldn't be considered spam. There's no link in the signature or profile of the poster or the post itself. A lot of forums allow for editing posts forever. My guess is they are just planting seeds for later editing when the thread is long buried and the only one visiting the page will be SE's. I haven't actually seen this happen yet but I am following a post on another site that was made about 6 months ago that I suspect was made for this purpose to see if that happens.