I'm out of step with most of the above, if there was a 'like' button, I don't think I'd bother with GN. I only post when I think I have something to contribute not because I feel the need to please an audience. I might just as well post on Twitter and Instagram and feel miserable when my posts are not 'liked'.
As to an 'Edit', button, the idea of being able to go back and change your post after posting could cause all sorts of confusion. I suppose that if editing changes were shown alongside the original text, that would appease some but somehow, further posts would have to reference the new 'changed' text or the original.
My positive suggestion for GN would be similar to book characters on Kindle, the X-ray function, where you select the name of a poster and you can see all their postings chronologically in a thread. So often, I see a reference to another poster but spend ages looking to see what they posted previously (that would include being able to see the original poster's updates too).
However, such a function should ever only apply to a single thread. I'm grateful that GN don't allow us to search all postings by individuals (at least, I don't think they do - I've never tried), their privacy would be severely compromised.