The part I was focusing on was the conclusion — that you don't mind others posting this question — rather than the exact reasons. I hope I got it right; please let me know if I should have done something differently.

(And I will probably have the 9-to-6 schedule for my non-mathematics job soon, so I hope others will step in and fill in whatever omissions in my own interaction with MO will appear: post related questions, edit my posts, tag my questions, etc.)

I kind of like the bounty idea, but (1) reputation continues to pour in after the bounty is offered and (2) you'll have to select an answer. I don't think you should make a separate dummy user for every possible source. If you just have one user named "Ilya's general purpose dummy user" I doubt he'll be confused with John Baez.

Creating a separate account for questions from TWF by John Baez is more risky compared to Joint Meetings as the possibility of confusion with Joen Baez himself is too high. As one possible solution, a poster can commit to give up all votes on the question as bounty.

I plan to use this approach for reposting questions from the Joint Meetings.

So they certainly pass the "don't make private things public" test :)

1. I posted Non-simply-connected smooth proper scheme over Z? from December comment remark by Kevin Buzzard and Minhyong Kim
2. I want to post the question I've heard about before + formulated by Qiaochu Yuan in comments to What’s the relationship between Gauss sums and the normal distribution?
3. I posted Killing the torsion in homotopy asked by John Baez
4. This is less direct, but anyway. I posted Why no abelian varieties over Z? as a question mentioned as solved long time ago by a paper.

It' clear that in all of these cases one should at least indicate the source, as I do, but it's not clear what to do with reputation.

Do we have any etiquette about posting other people's questions? So far, I'm doing the following, but it's rather inconsistent:

1. I posted as CW (because if original participants didn't post, they probably wanted to, but forgot; posting benefits all, though it would be more fair if original askers received reputation; and for me it would be certainly inappropriate to get reputation.)
2. I'm planning to wait a bit and see if Qiaochu Yuan asks the questions; meanwhile I'll prepare some background work and, if he doesn't post, I'll post mine.
3. I asked people not to upvote the question; it was not a CW because I wanted people to be able to upvote answers.
4. I posted as fully my question: I thought about something similar and took time to write it down carefully (this seemed well-received).

Do you have any suggestions?