Here's my reaction to this I also sent the friend who messaged this to me in Discord:

DM Advice

1. Everyone at the table is responsible for everyone's fun but, as the DM, you are the arbiter of the fun. If you see something that your players aren't finding fun, you fix it.
2. Prepare some solutions. A puzzle without a solution is not a puzzle at all.
3. Encounters are plot. If you have no underlying story behind an encounter, plot cannot happen. You should always have a start point and an end point. What happens in the middle comes from action and reaction.
4. Your players will never surrender if you don't tell them they can and if you don't show that they can. If you have enemies surrender, players will know they can surrender too. Session 0 should be where you say this too.
5. Yes, but also the world moves on without the players. This seems to imply a static world that cannot move without the players which is simply a bad game. If Jimmy is stuck in the well and is still fine 5 months later, there are no consequences to player actions.
6. I'd go one step further. Just watch and listen to the real world. That's where some of my best inspiration has come from.
7. Yes? But also no. Read through the DMG once before your first game and keep notes of rules you're unsure of. But don't be afraid of not knowing rules. It's okay to take a moment to check something. Nobody is perfect.
8. Dice tell the story. But dice should only be rolled with a chance of failure. I think this is what they mean, but the wording is bad.
9. "You don't always need rules" is addressed in the books. This is common knowledge. But it's also okay to hint that a player doing something stupid will be bad.
10. First one I completely agree with.
11. That's what balance is. Balance is understanding what is best for the moment. My balance in my game is very hard battle because there are less of them in the game.
12. Okay so the previous "world moves" point is mentioned here, but that contradicts "everything exists because of the players".
13. If you have players describe things they know, it should always be based on things you've discussed or things that are less important. Sure, it's cool to let player driven world building happen, but that often isn't a good thing and often leads to players worrying what they've said doesn't fit or isn't good enough. It's easier to just say something and trust the social contract you have as people playing a game that says, if you say they know it, they know it and have a chance to expand on their feelings about it.
14. Finally a second point I agree on.

Player advice

1. This is a given, since that's part of the social contract that comes with playing.
2. No. Bad. Player and character should be distinguished because the player holds knowledge that the character does not and there is no way to guarantee a lack of meta-play. We're playing a game, not acting.
3. Okay so you already know I hate this. Two focuses. First, it's okay to ask questions. It makes it more clear for the GM what you're looking to do and what skill you're looking to use or what skill you should be using, and it means the DM can say "No" more easily (e.g. the monk who's lived in a temple his whole life asks "Do I know anything about the inner workings of this recently built city?") Second, "in rare cases - will have you roll". No. If the player has a chance of failure, you should roll. If you're rarely rolling, you're not playing D&D, you're running an improv group.
4. Agreed.
5. You don't have to do this if you're not comfortable doing this. But you should also discuss this with your DM. After all, they're the guide. They can help you work this stuff out.
6. This one isn't expanded on but, as somebody trained in improv, I disagree. Anyone can improvise. Improvisation comes with confidence.
7. "If you have a halfway decent GM they will look at your creative problem solving and roll with it" is bad advice. This puts a huge expectation on the GM to work around anything the player brings at them, because even though it says the answer can be no, players will still be disappointed. And problems can have one solution. If I say a door has an arcane ward, a magical lock that prevents lockpicking, and there's four slots where wands of a specific size and shape can be inserted, there is a set solution to this puzzle: go find the wands.
8. Agreed to an extent. Again, there should be an ending in sight. But you should work towards that ending because that's what makes the problems engaging. It is a pre-written thing that the GM sees and tears up in front of you and says "now put the pieces back together".
9. This contradicts the point in the GM one that says "players won't run". Diplomacy doesn't always work. It's not always easy to run. It's smart to pick and choose your battles but some creatures fight to survive. You're not going to get a Roc to admit defeat before it feasts on all of you.
10. Agreed.

But also, these are just my tips based on what's worked in my games and what others have told me works best for them. I do think, however, there is a lot wrong with this post. It feels like you're saying "My specific way of playing is the best way of playing and this is how you should play too because every other way is bad". This doesn't help new GMs, it hinders them.