Hey so I decided to watch the first part of your LP. You didn't sound totally comfortable with commentating, but that's understandable because it's your first outing into LP. What I mean by that is your commentary is somewhat slow paced (constant filler words like 'um' show up a lot, and on occasion it'll take you a while to finish a sentence). Not only that, but to me commentary needs to fill a certain void, whether it be interesting/funny or insightful/clever. From my perspective you were playing it kinda safe and trying to explain the game mechanics and story while not cracking too many jokes. The way you handled it wasn't so captivating... like, for example, the one story you were telling about the friend who played Cave Story for the first time felt like it only needed only half the time to be explained. By the end of it I wasn't laughing because you weren't really concise with your explanation.
Also, your elaboration on the characters (like after you get the Polar Star) felt kinda forced. I guess if I could recommend trying something, watch one of your videos and listen to everything you have to say and pay attention sentence by sentence. Does this add anything to the commentary or are you just trying to fill time so it doesn't get silent? Alsoalso, have you ever thought about rehearsing before doing a take, or heck, even doing multiple takes if the first doesn't come out well? Commentating might be easier for you to handle if you cut the length of each part in half so, if you mess up, you only have to record another 8 minutes instead of 16 (and as a side note: post-commentary exists. So if playing the game is preventing you from making good commentary, try recording the commentary after the fact). Then when you become more comfortable with commentating you can try doing more at once. Another thing I should mention is don't be afraid to cut out stuff if it only serves to fill time (like the multiple attempts it took to get to that life capsule after Cthulhu's Abode). If you keep messing up the same part multiple times and your commentary isn't quite strong enough to hold the video on its own, cutting the mess-ups would prevent me from getting totally bored with it.
I noticed you just recently posted part 5, so I decided to watch the first 5 minutes of that too... oh god, the voices. I know it must be hard to commentate over a game with a lot of cutscenes that take some time to skip, but I can't really advise the use of cringe-y voices, lol.
BUT regardless, I always like to see an unknown face trying their hand at a Cave Story LP, so I do look forward to any future updates you may be posting here. Good luck, and I hope my advice was at least somewhat insightful : p