To put it another way... instead of "How can we encourage people who are playing this game to spend their time doing things they don't find fun?" the question could be "How can we create more ways for people who play this game to spend their time having fun playing it?"
I think figuring out how to get people to spend more time grinding when they might otherwise quit out of a feeling of ennui isn't the right question to answer, and there's no version of it that is. Games are played for fun, in theory at least. Positive reinforcement for grinding instead of playing can sustain an illusion, for sure, but that's like how if you make it slippery enough, you can get your car down the road without any wheels on it. It's a solution, but not the solution.
https://www.verywellmind.com/difference ... on-2795384 I found this article while checking my memory on what I mentioned earlier. The principles seem to apply, and I think more game designers could stand to study it more, since a lot of games die off not because the players didn't like playing, but because they were taught to wait for top-down feedback on what they were doing instead supplying their own.
Speaking of which, journals, chronicles, or scrap books are all ways to keep records of a character's progress, but the game has no automation for any of that. I wouldn't press for it, but if it simply printed to a logfile every time some sort of event occurs related to character progression - the same ones that the client itself gives immediate feedback for, like stat increases, skill purchases, and so forth - that'd serve as a basis for something to show off, and to be examined. Could be useful for the data and insight, not just as a keepsake. It'd be raw, though, and need some kind of processing.
Which brings me to the next idea. Based on what I've heard from them, from the beginning and on through today, Jorb and Loftar created Haven & Hearth because they wanted to see what players and the communities they build would create and come up with. They don't want to tell us what we should and shouldn't do in game. That doesn't mean we can't have external rewards for what we do in the game, but it suggests those rewards should come from the community, that members of the community should decide trophies, prizes, ribbons, or whatever else should be created and awarded to players, and who they should be awarded to. Maybe if one or more of those rewards get prestigious enough Jorb and Loftar might implement an in-game version to apply to an account just for fun, but it makes no sense to start there.
We could have a discussion about what in-game feats or achievements we as players would like to see other players commended for, and what would seem like fitting rewards without the need to program them into the game, first. I don't have much to add to that since it's not something I'm interested in, but there's nothing to stop players from creating and adding ribbons and commendations to their forum signatures, for example, except that it might be a bit tacky to do that without coming up with some kind of broadly-accepted system for it first. Has to start somewhere, though.
In short, we can make our own trophies and achievement milestones.