Checking the Android Market reveals a couple of "User Dictionary" managers/editors that allow importing/exporting. Unfortunately (which you probably already knew) they state they will not work with most (all?) HTC Sense phones. Drat!
I've found the User Dictionary located in SDCard/.data/HTC_IME/UserDictionary -- it can be pulled up into a text editor (I used Office Pro in text mode) but I don't think you can modify/save in text mode and have it work. You could make a backup of your Personal Dictionary (Settings | Language & Keyboard | Touch Input | Sync personal dictionary) and after the backup you could try editing this file with a text editor and see if it works. If not, you can restore your backup via the same menu path as above. Something to try anyhow.
-Frank