I have used the Nookazon discord dozens and dozens of times for trades. I use it when I want something fast or want something gone fast. I actually like the community, but it's usually very much an in-and-out kind of thing. And yes, the prices can be insane. Any cherry-blossom recipe, mush lamps, or the bonsai shelf can sell for upwards of 30-60 NMTs. I bought 2 mush lamps for 3 NMTs each and I thought it was a pretty nice deal lol.
If you trade on there: FENCE OFF YOUR ISLAND!!!! This is such a huge deal. Fence off an area in front of your airport. Get a stall customized with a trading post sign and put it right outside. This will get rid of 99.9% of griefers. There have been multiple times where I trade and then afterwards, the other player sprints towards my stores/flowers only to realize that they are fenced off.
Make sure you have your game open if you trade. Don't wait too long to open your gates or ask people to hold stuff for you. If someone is providing something for free like Saharah, tip them 1-2 NMTs or something else. It's just the polite thing to do.
I wouldn't be scared to trade on there as long as you fence off your island and know about airplane mode. Also, keep in mind that there's a ton of little kids and teenagers on there too. I used to use the acnh-discussion a lot, but then I realized that most of the people on there are just 14 year olds who start drama. TBT is much better.