When someone takes the time to answer a question, it's nice for that person to feel recognized and that they were helpful. While seeing upvotes is a good indication that the answer was helpful to the community in general, there's not any indication that the answer was specifically helpful to the person who originally asked it, as the asker's upvotes are just mixed in with the rest of the community's.
I certainly think that it's fine for there to be no concept of a single "accepted answer" controlled by the asker. However, I think that there should be some sort of way for the asker to recognize and thank the people who wrote helpful answers for me. This leads me to a bit of a conundrum:
1. Should it be correct etiquette for the asker to leave a comment saying "Thanks" or the like on helpful answers? This was certainly discouraged on other Q&A sites I know of, though maybe it's the right answer here?
2. Or, should there be some way for people (maybe just the specific answerer, or maybe for everyone) to see that the person who originally asked upvoted their answer?
I could brainstorm some other thoughts too like some dedicated "thank you" button or the like, but what makes the most sense in my first pass at the idea anyway is just adding some indication next to one's own answers that the asker upvoted it, and maybe some notification which could end up being some sort of standardized "thank you" for the experts who write the answers in a community.