For years (literally) I've been
looking for an EASY and reliable way to edit, backup and restore my T9 dictionary. The myT9 app that installs with some SIPs is decent but there are a few inherent problems with it, for one it's got to be modified using your mobile device and the big issue is that you can not backup the custom words you've entered.
Poking around inside the OEM for one of the newer Diamond 2 keyboard releases I came across
the HTCMDB.txt file and did a few tests to see if the common online phrases that HTC included could be used to supplement the standard English list of T9 words and I am thrilled to report that not only does it add those words to your dictionary but much to my surprise
you don't even have to flash to get them to show up, in my latest test I didn't even soft reset.
So, grab the HTCMDB.txt file out of your Windows directory, open it up in Notepad (PC) add one word per line until you've got all your common words stored, save and write the file back to the phone -- keep a copy on your Desktop or Internal Storage, for future flashes and you'll never be bothered reloading all your names, slang, swears, etc. again!
Rebuilding my dictionary is THE single most time consuming thing I have to do after a flash, pretty stoked about not ever having to do it again.