I'm a freelance copyeditor, and I've worked on a few TTRPG projects in the past. I'm looking for more projects to work on to help me fill out my portfolio. You can see past work I've done at www.pagesofkenna.com
English is my native language, and I've recently completed a course in English grammar and copyediting. I really like editing technical documents, which includes game rules. I'm good at catching when rules don't make sense, or interpreting what you're trying to say and figuring out how to make it more clear.
I also enjoy playtesting. It can be as light as me giving you my impression of your project, or as detailed as me recording my games and letting you know how it worked out move by move.
While I'd love to be paid, I understand we don't always have the budget for that, and I'm willing to work on a volunteer basis in exchange for a testimonial I can add to my portfolio.