This is borderline acceptable to me. It's not a drastic change, but I can see why people would reject it.
I might instead post a comment saying something like ("This piece doesn't seem clear, perhaps you could say < insert new text >""This piece doesn't seem clear, perhaps you could say <insert new text>."). Often the OP will edit in himself or say you can do so. At least the OP has some input in the matter.
In general, you don't change the content of a post in an edit. Doing so can change the solution or problem. You were just clarifying (and did so well), so it's borderline. It is something to keep in mind for the future though.