It could simply be a temporary browser or computer glitch, especially if you’re seeing text or activity that you don’t remember posting. I’d check your account’s recent activity and
visit website pages carefully to make sure there aren’t any replies you didn’t make. It may also help to clear the browser cache, restart the computer, and make sure your browser is up to date. If you only replied to one post today and your account activity confirms that, I wouldn’t worry too much. If the strange behavior continues, changing your password and checking your account security would be a sensible precaution.