after posting a reply, the next time i open my browser the text of my reply remains

While it's normal that your text input is remembered if you don't submit your reply before closing the browser, the reply box doesn't seem to get cleared out after making a reply so your reply text gets saved even after you've already replied. This has occasionally led to an awkward situation where I re-post a reply because I figure I didn't actually submit the first time, when in fact I did.

I'm actually not sure if this is specifically a browser feature or if it's a forum cookie or something.