@Pupi... I also have one user out of 10 who cannot see the full wysiwyg editor and this is under the snow theme.
Quoting the user's feedback to me.
"I can add a question title but where it says enter more details for your question below... Sometimes, there is a text area box but I can't enter text and sometimes, there is not even a text box?"
"I access the site from a desktop pc and I am using recent versions of IE and or Chrome browsers (I have java enabled?)"
Since only one user had this problem and I couldn't replicate the issue. I thought is must be a local/isolated problem and didn't report it as a potential issue. However, James's post now suggests that maybe there is something amiss? Your link to Sama's fix. Did not solve the issue for my user.
Since the same user can post via markdown, I've set that as the default editor for the whole site now to resolve the seemed one off problem.
Hope the feedback helps?
P.S. Using 1.7 beta