It happens to everyone that refreshes the shoutbox after they've posted. Just go onto another page to break the loop.

And a mutual gainer wants to gain weight themselves at the same time as the person they're teamed up with does.
A feeder is someone who feeds someone. A feedee wants to be fed and/or gain weight, often with the help of a feeder.
To stop the message repeating, go onto another screen instead of refreshing the page.

I'm hanging about in there, though it remains silent. People are busy with celebrations currently, I suppose. ^_^