Brainstorming possible reasons off the top of my head:

The fact that I can brainstorm possible reasons doesn't imply that I know the reason. Asking people for the reasons of their actions is helpful for having rational discourse.

I completely agree that my comment was of low quality and its present score of -3 seems pretty reasonable.

I'm worried that one aspect of its intent may have been misunderstood. (It's entirely my fault if so.) Specifically, it could be read as mocking ciphergoth for, I dunno, not appreciating how consistently useless Steve Fuller's writings are or something. I would like to put it on the record that nothing like that was any part of my intention. ciphergoth, if you happen to be reading this and read my earlier comment as hostile, please accept my apologies for inept writing. My intended tone was more like "yeah, I agree, isn't it terrible? But he's always like that" rather than "duh, so what else is new? what kind of an idiot are you for thinking he might be worth bothering with?".

For the avoidance of doubt, this isn't an attempt to argue against the downvotes -- they're deserved, it was a crappy comment, and I'm sorry -- but merely to clear up one particular misunderstanding that, if it's occurred, might have worse consequences than losing a few karma points. (Namely, annoying or even upsetting someone I have no wish to annoy or upset.)

shminux: I'm not sure that "low level of discourse" actually tells me anything -- pretty much every good reason for downvoting a comment comes down to "low level of discourse" in some sense. In this instance I'm pretty confident I grasp all the things that were wrong with what I wrote, but if you were intending to provide useful feedback (rather than, e.g., to say "boo!" a bit louder than a downvote does on its own) then a little more specificity would have gone a long way.