Dear List,
In order to verify the mechanism with a French document, I have set
the code sample given by Wolfgang for paired boxes with align
footnotes through French language commands. And I have substitute 2
French texts to 'Content' (after removing previous \input tufte and
\input ward), and fill the tables titles with my own. All is fine,
except hyphenation which seems to be an issue here : see in the
first text the word 'automatiquement'.
The missing hyphentation has nothing to do with floats, footnotes or
paired boxes but a result of the default alignment setting for natural
tables. To change the default value for the alignment you can use the
align key for \setupTABLE.