Expected reputational damage is probably $a few hundred IMO. It could be picked up and used as ammunition against SIAI.
Few will care about a silly comment on one post, especially given the context. Anybody using it as ammunition will look really petty.
Better ammunition:"But when Eliezer was counterfactually mugged, he didn't pay. How serious is he on his decision theory?"
Even if the procedural problems here give him a good reason not to 'pay', paying is better rhetorically. (though he may clarify that he won't pay under similarly sloppy conditions again.)
I'm going to test just how much the people here are committed to paying a Counterfactual Mugger, by playing Omega.
I'm going to roll a die. If it doesn't come up 5 or 6, I'm going to ask Eliezer Yudkowsky to reply to this article with the comment "I am a poopy head." If I roll a 5 or 6, I'm going to donate $20 to SIAI if I predict that Eliezer Yudkowsky will post the above comment.
Because Eliezer has indicated that he would pay up when counterfactually mugged, I do predict that, if I roll a 5 or 6, he'll respond.
::rolls die::
Darn it! It's a 5. Well, I'm a man of my word, so...
::donates::
Um, let's try that again. (At least I've proven my honesty!)
::rolls die::
Okay, this time it's a 1.
So, Eliezer, will you post a comment admitting that you're a poopy head?