Just to be clear, the root node showed output from Data::Dumper that could have clued you in that there were no carets in the strings. And at least two replies made this point very explicit quite a few hours before you posted despite your claim that it was "a finding published later than my post".
Your mention of:
Posts on this site occur in chronological order
makes me suspect that you are referring to the order in which direct replies are sorted when displayed in a thread and that you made your conclusion based on the order displayed and that you didn't bother to glance at the timestamps (nor did you look carefully at the replies before originally replying).
And your confusion on the timing makes me suspect that you were seeing direct replies sorted "newest first" (reverse chronological order). The site has long offered sorting of direct replies oldest first, newest first, or highest-reputation first but only recently was a bug fixed that meant "newest first" actually resulted in "oldest first" before that. So several people suddenly had their note order go from "oldest first" to "newest first" when that bug was fixed.
Given the number of complaints, I began to suspect that perhaps the bug fix was actually impacting people who had not previously changed their User Settings to select "newest first" (and left it that way). Your reply was the straw that induced my camel to actually try to verify whether that was the case. I couldn't find evidence of that (Anonymous Monk sees nodes sorted chronologically and has no value defined for that setting and an old user that I'm pretty sure had not modified that setting had the default value and also sees nodes sorted chronologically) so I guess that fiddling and picking "newest first" (and leaving it) is just more common than I'd have expected (though there certainly could be more to it than that, just not something I was able to discover with my simple tests).
Anyway, I hope that clarifies some things.
In reply to Re^4: Subtracting Stringified Negative Numbers (carrots)