> The same goes for Scheme code. If you have found something in `format'
> that is not thread-safe, do let us know.

Well, apparently for format this was already known, see the last sentence of this old msg from Marius Vollmer :

http://www.mail-archive.com/bug-guile@gnu.org/msg01949.html

But if you want an entry in the bug tracker I can add one :-)