> I think knowing when an ID was created is harmless - and if it isn't there is a design problem that is larger than ID choice.

I hope you're right, since I've been cautiously operating under that assumption so far. Cautiously, because of warnings, from people better versed in cryptography than I, in discussions like this one: https://news.ycombinator.com/item?id=29805433. I still haven't quite been able to internalize when this should vs shouldn't be something I should be concerned about, hence the comment.