In T5993#201111, @werner wrote:

For example Poppler uses GnuPG comment packets to lower its own attack surface by leaving all OpenPGP handling to gpg. The patch (or at least the version we noticed in Fedora and Debian) entirely breaks this use.

btw, my clue was that in that last --check-sigs, if i used --debug-all i got this:

This affects certification-only primary keys when doing web-of-trust calculations.

To avoid further noise on this ticket, i've done as requested and posted to gnupg-devel : https://lists.gnupg.org/pipermail/gnupg-devel/2025-May/035875.html

A bit more experimentation shows the same behavior, even if Alice's tsig of Bill is full, not marginal, and even if all signatures are made in the same second, which is the finest resolution that OpenPGP objects can report.

Interesting analysis, thanks for the sleuthing! I'm not sure i understand why "the latest" should be preferred. For example, in the graph made in this example, which part of the graph is the "latest"? Since the path from Alice to Carol is two hops long at least, it's conceivable that one path (A→Bob→C) has both "the latest" tsig *and* "the earliest" tsig, if the other path (A→Bill→C) happens to have been made between the other two tsigs.