Mine is a testnet address for people on testnet versions of clients like mostard (not sure if it has a testnet implementation but Garnet does)

Now that you bring it up, I'm not sure why I don't use mostard. It's a good idea for a client and I've tested it before, but for some reason I can't quite process, I still don't feel comfortable accepting money for my posts.

I guess I just don't need the money or deserve it, but in that case I should accept tips just to send back out to other people and add to Monero's anonymity set, but in that case I would run into psychological obstacles like greed or getting into a fight with someone who changes their mind about me and wants their money back.

I'll keep thinking about this.