That's what that was! I experienced this behavior for years writing posts or comments on facebooks mobile site, helped me a lot to wean myself of that one.
Yes! I had something like that and it was so frustrating I wrote a post (on FB, sigh) about it, looks like it was August 10.
I had written a comment with multiple paragraphs (which I guess they don't expect people to do, or test for) and I wanted to add something to the next-to-last paragraph, and when I tried to type "matters" it would keep locking me in autocomplete tagging for friends name "Matthew", and as soon as I dismissed the cursor would leap to the end of the comment. If I tried to click back, the cursor kept jumping to the end!
