Hi JonnyGamer! 
You’ve thought a lot about addressing this! I think it’s not available in the forum where we are — but there’s a feature where Discourse automatically summarises long topics to show the “most interesting” posts, calculated according to post read time, number of likes etc
You can see this in long topics (random example of a long topic here, there is a Summarize This Topic button at the end of the first post)
But having votes is an interesting idea & marking important posts on the scrollbar 