You're looking at the wrong post. The one in which I made these comments is stamped 11:36; the one (of mine) to which I was referring is stamped 11:17. I couldn't really know how mine was going to be stamped before I sent, could I? :-)
No. There is no setting in Thunderbird for this kind of stuff, and the information we're talking about is right there in the message headers. And threading will only overrule time stamps if I'm looking at the threaded view. If I sort by timestamp then threading plays no part in the sort order, and that's where the problem shows up. Recall that I'm not the only one seeing this problem.