sarah_TO said:

There is a difference between no evidence and evidence of no effect, and this subject is one where the two get swapped freely in both directions.

Reprising the part of this that the last few posts have moved away from:

Take it one variable at a time. Almost every unanswerable question in these threads is unanswerable because three things changed in the same fortnight, and no amount of subsequent argument can untangle them after the fact.

Coming back to something from earlier in the thread, because it keeps being talked past:

Take it one variable at a time. Almost every unanswerable question in these threads is unanswerable because three things changed in the same fortnight, and no amount of subsequent argument can untangle them after the fact.

Reporting back.

Closing the loop. The answer turned out to depend on the detail I had left out of the opening post, which is a lesson about how to ask rather than about the subject.

Admin said:

The answer turned out to depend on the detail I had left out of the opening post, which is a lesson about how to ask rather than about the subject.

Filing a mild objection. Mild because I might be wrong; an objection because nobody has addressed the case that does not fit. This treats a plausible mechanism as a demonstrated one. Plausible is where you start looking, not where you stop.

I would rather be corrected than agreed with, if it comes to it.

Admin said:

The answer turned out to depend on the detail I had left out of the opening post, which is a lesson about how to ask rather than about the subject.

That is right, and it stops being right at the edges. The general case is well behaved; the interesting cases in this thread are all at the boundary where the general case breaks.