Not point of OP but wanted to say definitely no to a downvote system. It will absolutely get used to promote an echo chamber, and at least given a situation thinking outside of 'yourself' (self-aware is more difficult to do consistently) I think everyone can agree people hivemind and then that becomes scary as well as often hiveminds can absolutely be wrong. To the point of hiding actual information because of a group of people keep passing around false information or controlling the narrative, made worse since when you post you might or might not get an accurate representation of the situation (maybe one time you post and a group of people who hate your idea hide it, but on an average day the majority would have liked it- it's like the magic of posting your content at the right to time activate the windfall of interactions). Absolutely no to a reddit like system, it makes echo chambers every time all the time - which is good if you're dedicated around kittens or something and people have that mindset, but obviously can go poorly. Often you'll see reddits with an unspoken rule of acceptable utterance and conduct that is enforced by the majority, no thanks when trying to foster a community of sharing feedback.
Plus I trust SE more to read what people are interested and approach that more logically than players determining what SE can or cannot see, which is why I'm fairly outspoken when I see people try to shut down conversations for perceived reasons ("can't do this because of this one story element or accounting financial reason, etc", I feel is counter to the point of the forum), SE knows if they can't do something because of their own story, financial means, or what have you, what they don't know as easily is what and why people want stuff (desires and feedback)- even if they wont do exactly what a player wants they would gain far more useful information if you had just let the player explain and share their desires over silencing the conversation.
As for the forum I think our current system is fine, although I wonder what would change if even the likes were hidden (from us, not the devs of course). I feel some people use likes as a way to actually read content, if something has likes it has a chance to get more likes, which may draw attention to something they would otherwise not read.. which may be a good thing.. but at the same time that means people might be skipping something they would have actually agreed with simply because they didn't get the right 'windfall' at that time. Some starting the like storm.