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...?'
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.