A like button seems like a popular choice, so I can't see MN implementing it any time soon. They don't seem to add things posters want. Again suggested threads and my feed being perfect example of this. 
A sub-comment/reply structure like reddit, so instead of typing the exact same thing with extra nuance someone can just add their additional thoughts underneath an existing comment.
This is a good idea and would help prevent threads from going off topic.
As I mentioned above when premium frost came about one of the things they mentioned was an edit feature, it was a good hook as they know so many people wanted it but it's still not made an appearance years later.
I wonder if we'll ever get an update from MNHQ on the edit feature.
But, overall, I'd prefer fewer options tbh, not more, can do without quoting and gifs and non-MN emojis.
I agree with you about GIFS, they add nothing to the discussion and take up a lot of space on a thread. However, whilst I don't think we need to add all the bells and whistles, basic features like quoting, emojis and editing have been around on forums for years and it's unusual for a forum to not have them.