Text gets highlighted and deleted while typing
Every so often when I'm typing in a reply, the last several words I typed will be suddenly highlighted then immediately deleted. "Undo" doesn't replace the deleted text. When I try to re-type the text I deleted, sometimes the same thing happens again after the same letter of the same word, and sometimes not. It could be that it's being triggered by some particular combination of letters or words, so if I don't use exactly the same wording it doesn't happen? not sure about that.
This happens once or twice in every forum browsing session (twice in the last 15 minutes). This doesn't happen on any other site I visit, or in word processing or other software, so I know it isn't just user error.
What's going on? Is it some sort of filter detection?
Using Safari on a Macbook Pro