Oh. Yeah, I did start a little discussion on an isomorphic trick in Umineko. In this case, the date on which I posted the hash is provided automatically by Reddit/Lesswrong/Twitter/etc and one can also verify I didn't post any other hashes recently to those fora.

The trick also only works for 'small keyspaces', if you will - if for example I was trying to fake a precommitment to a 100-digit number, the trick isn't going to work because it's not feasible to publish precommitments to even a tenth of the potential 100-digit numbers without people noticing and calling foul - 'so, gwern, why are you publishing that many precommitments and when can we expect them all to be revealed...?'