Pretty much any interaction with the comment box creates highlights between two words. No matter how you tap, it’s nearly impossible to just have one single cursor. Sometimes it’ll shrink to a single space, but that’s about it, and it’s been like this quite a while.
Typing this post, I’m able to just tap and move the cursor, but if this were a comment, it would create a highlight between where it is, and where I tapped next, every time.