I noticed that they have added a delay in the share buttons being displayed. I guess some people have not been reading and only sharing instantly.
If you scroll down to the bottom (which you normally will when you read and comment) and then wait a moment, it will normally appear. There is a bit of a delay though.
If not, I find sometimes that I have to return to the top for it to appear (depending on what device I am using to access the internet).
Hope it helps,