Editing the hints.txt file in those programs may or may not be fine, but I find that too often editing a file that will be read by another program in anything but a text editor designed for programming will somehow throw a wrench into it all.
Take phpbb files for example, they need to be encoded in UTF-8(w/o BOM), not UTF-8(w/ BOM) like notepad and wordpad encode in. You screw up a lot of work in wordpad once and if you're like me you'll never use it again.
Besides, notepad++ for example has a lot of cool features to make your life easier and if it's just as free, why not.
As for OOo's Writer, I like it a lot, a lot more than I like MSO's Word, but I only use it for actual documents that I'll be printing out or something. I generally like to stick to .txt for everyday use files as they're small in size and simple.