Having the friend's list organized in alphabetical order or something would be better.
Currently, it's done by order of most recent activity, which is why it needs to reload constantly. But I don't get much from having it in this way. All I really use my friends list for is seeing who needs quarry help (and market box if I'm desperate enough, but given there's a symbol to tell me if someone's market box is empty or not, I don't need to use the activity to judge this either).
Long story short, the way the friend's list is organized means it HAS to be reloaded constantly, but there are much, MUCH better ways to sort it, most of which will avoid this need for loading.
In the case of bulletin board could be a tricky subject and could work for both sides - leaving notes and being rude. Given the OP mentioned wanting to use it for avoiding ultra-rare sellers, perhaps a greeting message would work instead. A player chooses a greeting message that is delivered to a new friend whenever one is made. Horrid greetings can be reported and forces the message to be changed (to nothing or to a default message). This would stop the possibility of someone going to every campsite they can find and posting "haha ur campsite SUCKS" or whatever - one greeting message, one report, one delete and the issue is sorted. That's the best resolution I can see that solves both issues at the same time, HOWEVER, in this case, I do agree with tolisamarie, we need a way to be able to communicate with other players better, and the solution I suggested does not help with that very well.
Maybe not essence trading, due to it being a reward for interacting with certain villager types, but TOTALLY trade with the other crafting mats. I need 5 preserves, Bob needs 5 wood. I have 5 wood, Bob has 5 preserves. Easy solutions - TRADE!
A third amenity spot would be great, or campsite space upgrades in general. I would be happier if the loans in the game went into growing the campsite instead of camper vans, as I know very few people who actually care about their camper's interior. (I actually do myself, but I feel like one of very few, looking inside the campers of people I meet in the recreation zones)
My own suggestions:
-Add more cotton droppers. The need for cotton is great when it comes to amenities (each tent needs 30 per upgrade, that's 90 per tent, that's 360 for all tents, and the picnic set needs 30 too, 5 levels is another 150, so 510 pieces of cotton for these 5 amenities). It's a frustration getting so much cotton. I get upgrading amenities is supposed to be a challenge but the issue is I still need cotton for furniture as well, and only 6 characters in the game always give it out after requests. I'm lucky if I see one of these 6 in my request cycles a day. (In case you were wondering, it's the two penguins Tex and Roald, the two lions Rex and Bud, and the two pigs Maggie and Agnes). It's just super hard to get your hands on and needed so desperately.
But in all seriousness, I think they've done well so far and I'm in love with this game.