Any particular reason why comments constantly shift on a meme? After awhile threads don't make any sense. Is it points?

They're ordered primarily based on upvotes, and secondarily based on alphabetical order, if I'm not mistaken.

If you see a comment that seems to have more upvotes than a comment above it (at the same nested offset in a thread), that means it has downvotes that aren't actually visible.

Pretty sure you are right, except the alphabetical order thing. I have never heard of that. Though I guess it sounds like something they would do around here. I wouldn't put it past them.

It may have changed now that they've added time posted to the comments, or the downvote effect, or it may have been pure coincidence, but whenever I wondered why some newer comments seemed to be above others that were older and that had the same number of upvotes, they always seemed to be in alphabetical order.

The down vote always moved comments downward, and eventually to hidden. Well, for as long as I have been paying attention at least. But I always wondered the same. I went looking through some longer comment threads and just when I thought I found some sort of rhyme or reason to the order I would come across something to contradict what I thought they were doing. It is strange.

Ordering by most upvoted helps drastically with promoting higher quality comments. Either a "sort by latest" or "highlight latest comments" button is something we could add though.

THAT would be awesome!

More upvotes moves to the top of the thread. It's sort of like frontpage where more people see the most upvoted and it snowballs. I'm not saying it's a bad system but it definitely skews things when certain big accounts get guaranteed upvotes from their fans which pushes their content in front of more faces than the average account can muster.

They go based on how many upvotes and downvotes they get. The ratio... It's better thatbway because if the majority of the community doesn't want to see them, they get pushed back.

Regarding "making sense" though, the primary mechanism for making the comment stream sensible should be using the "reply" button, which guarantees that a given comment will come after another one. If a comment is not a reply, then that means it should be a parallel comment, not necessarily occurring after any other comment.