TextMate is a pretty cool editor (where is 2.0!?!) with good supports for editing a bunch of formats including e-mail-style text documents. Part of this support is a “Reformat Quoted Text” command which uses the
par command to wrap text while maintaining line prefixes and suffixes. Alas, the version of the
par command that ships with TextMate is for PPC Macs.
This means that to reformat quoted text you must either be using a PPC Mac (ha!), install Rosetta (HA HA HA!), or fix the command. This last is both the easiest and best of these options.