A sent message brought back by Undo, Cancel and edit or edit-as-new
reopened with the default label, because only drafts carried the
X-Bulwark-Label marker; it now falls back to the SIO-Label it went out
with. A reply, quick reply or plugin forward takes over the original's
label only when an internal sender set it and never one below the
default, since anyone outside can write the header. The tests written
for the earlier rule (any received label counts) now pass an internal
sender, which is why their originals changed.
Linus Rath