Ah yes, I hadn’t thought of that. But then I’m happy to use Word to share any changes that have to be marked; I just like Kaleidoscope for its speed and the clean view without the formatting.
For one client who wanted hard markup, I used to use a Nisus Writer Pro “compare documents” macro created by the legendary Kino. As a way to show changes clearly, as opposed to accepting or rejecting them, this worked very well. For instance, IIRC you could choose to compare at the level of characters, phrases, sentences and paras. Contrast with what happens when you change a letter in Word: sometimes the change is marked as one letter, sometimes as the whole word.
Good luck in finding something that works for you. I use Markdown whenever I can, but I don’t mind Word and for paid work I’m pretty much obliged to use it.
Yes, even old AppleWorks files! I stand by my assertion that it’s a clunky app for everyday use however. Very un-Mac-like. Hard to argue with free though, on top of the Swiss Army knife features!