Sooo... nitpicking I know, but a Mary Sue is an original character that is written into a fanwork and is somehow perfect and beloved by pretty much all. Although CVRPG might be based on the Castlevenia games, it really doesn't seem to be so much a 'fanfic' Its not only one or two original characters, its most of the cast, especially at this point. In that way its as much a fanwork as Sherlock the tv show is to the original book. That being said, Darkmoon is fallible. Despite what competence he's been showing lately, I'm certain he'll make more blunders soon and if nothing else he was a dead beat dad. Katrina is probably plotting out ways to painfully maim him, even. Claypool really doesn't seem impressed, and in some ways having Angel like someone is more of a downside than an endorsement. Ergo it might be just my opinion, but Darkmoon really doesn't seem like a Mary Sue to me, or even a Gary Stu (similar but male)

Technically a Mary Sue is a PERFECT character with no flaws who doesn't grow within the storyline. MauLer had a great breakdown of the Disney Star Wars abortions and why Rey is categorically a Mary Sue and such a shitfest of a character. Check out his YouTube videos on Star Wars. He does a great job explaining the mechanics of poor writing. I watch to improve my own ability to story tell.