The other day I faced exactly the same problem you are facing here: I totally missed a text link. I was looking for an edit button in a special page only moderators can edit, and I had to look for that button three times until I found it.
You just need to notice the text link saying "show preview" just under the edition window, click there and you'll see the preview. The funny thing is that here in Meta that text link does not show up, and I can't remember having seen that text link before, so I guess it is easily missable (does that word exist?). And another thing, you are not the only one. It seems also that the preview setting is stored per site, which explains why you can see the preview in other sites but not here. As Glorfindel said in the MSE question, maybe you clicked in that link by accident.