EditPlus is paid...
Okay. Here are the issues I'm having with various text editors. Italicized is its status with UTF-8
UltraEdit-32 8.00 (editor of choice) - This version of UltraEdit appears to only be able to switch from ASCII to Unicode. Binary analysis seems to indicate that it uses USC-2 and a BOM (kinda required). Copy paste does work, but it doesn't save as UTF-8, so I'll need to program something to switch it to UTF-8. I think it doesn't have UTF-8 support.
No support
Crimson Editor 3.70 - I have a file opened up in UTF-8 mode without a BOM. I have FireFox (great unicode support, by the way), displaying a character correctly. When I copy and paste into Contact.html, it gets replaced with a ?. Trying to type it in ALT+number yields the wrong character. All other modes yield similar results. Perhaps it doesn't have intelligent font matching? Nonetheless, saving the file and then inspecting it in binary mode seems to show that the ? are ? and nothing more.
No support
Gvim - WTF.
So unintuitive...
jEdit 4.2 final - It doesn't appear to be smart enough to mix and match fonts (big bummer for Chinese writing... you'll have to switch to SimSun or something) BUT it has full support for Unicode (the blocks are still the characters...) and lots of other encodings. It doesn't add a BOM for UTF-8. Very nice, actually.
UTF-8 support without BOM, but no font mixing
Notepad, bundled with Windows XP - Now, notepad is very funny. Supports font mixing. Handles UTF-8 well when displaying. The problem? It adds some weird BOM thingy... EF BB BF when you save.
Font mixing, but adds BOM
SVN - Not sure about the implications... UTF-16 probably needs to be sent in binary mode (meh).
None of these does exactly what I want, which is:
* UTF-8 support without BOM
* Font Mixing
In the end, I think the font-mixing capabilities of Notepad will trump, and I'll just make sure PHP trims off the BOM when it is present.