If you make a new repl, (e.g. by visiting https://repl.it/languages/csharp) it immediately saves it and puts it in your repl list. I often click the wrong language, or open a repl in a new tab and forget about it, and my repl list fills up with dozens of "blank" sessions that have never been edited.

I suggest that a session shouldn't autosave until it's had at least 1 edit, or until it diverges from the default template, or something like that.