Doh! Login state was the issue—sorry about that. Juggling multiple computers and browsers, and I missed being logged in on the secondary browser on the secondary Mac. 
However, my comment about the triple-click issue remains. This may be Safari’s problem since it happens in Safari 18.6 and 26.0, but not in Arc, at least, when I triple-click to select the last paragraph in a post, the Quote button doesn’t appear.
If I select that paragraph carefully to avoid getting whatever line break or carriage return is at the end, it works fine.
And if I triple-click to select something other than the last paragraph, it also works.
