You've handled it well, so far. The abandonment sentence was well thought out.
The fun thing about the court system is that anyone can sue for anything. There's no requirement that the complaint have merit for it to be filed. Now, that said, if a complaint is meritless, there are court rules that allow you to make it go away pretty easily. The Court is also allowed, in some cases, to kick the complaint out.
If it proceeds, your emails present a pretty good defense. Assuming your forum name is descriptive and that you're a business, read up on the Uniform Commercial Code (UCC) sections 2-601 through 2-608 and 2-711. UCC
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