I'm not sure why your comment disappeared when disabling rich text. I haven't been able to replicate it – I'm also using OSX and Chrome (26.0.1380.0 canary).
We just published a fix for the whitespace a couple minutes ago, so replying to comments should be easier now. I think the whitespace was there for all browsers, unfortunately. I was hoping to get that fix out before anybody posted but I was a little too late.
After clearing your cache (if caching is enabled in your browser), please reply to this comment & try switching off the rich text editor again. I'd like to find out if that was a one-time occurrence, or if it happens consistently. I can't get it to act that way. But clearing the cache might help.
In just a couple weeks I'll be able to focus my efforts to improve things on xTuple.org. It's long overdue.
Thanks for hanging in there.