I think that this passage reinforces my interpretation of Thranduil as more of a wood elf in character than the Thingol-like image the dwarves seem to have of him. His cave may be his stronghold and a refuge for his people in time of need, but Thranduil himself does not seem to have much regard for stone or for anything mined from the ground. He owns jewels but forgoes them in favor of leaves and berries. He has stone but chooses to sit on a chair - not a throne, a chair - of wood. With his crown, his staff, his chair...Thranduil seems to take a lot of influence from his wood elf subjects. Certainly he doesn’t seem like the sort of person to disparage their culture and consider them lowly Silvans...mind you, I haven’t seen the Hobbit movies, but I have heard. Some things. About their portrayal of Mirkwood’s king.
Anyway. I think we could use the lack of information about summer and winter crowns to explore Mirkwood culture a little in fandom - since we know so little about it. I figure either spring and fall are special seasons to the wood elves. Given his rather humble way of dressing, I wonder if Thranduil even wears a crown in summer or winter. Or perhaps those seasons are the significant ones, and he wears formal crowns then? But I don’t get the sense that wood elves have the same ideas of formality as the rest of middle earth. I’d love to see someone play around with some of these ideas in fanfiction. I think the Thranduil I’ve seen in fandom is nearly entirely based on the movie version. And I’m not condemning that version - clearly it was impactful for a lot of people - I’d just love to see book!Thranduil reconsidered.