There’s no harm in leaving a forwarding address when you leave a place.

Additionally, it’s a common practice for some users of reddit and things like it to click over to the profile of someone who posted something you find interesting; why not check out what else they post or are into? Now whenever someone clicks OP’s profile the first thing they’ll see is this, and that’s potentially of value to someone over there who hasn’t yet checked things out over here. Old reddit posts and commments still get new engagement coming in all the time even years after the fact, so something like this can actually reach folks.