Temporary fix for invisible posts or guides ( https://i.imgur.com/F5yyCna.png )
Sorry for double posting, but it's the only reliable way to communicate.
Apply a CSS extension to the site, and add the following rules:
form[name='newpost'] > span { display: block; }
form[name='editguideform'] > span { display: block; }
This will make the posts and the guides look like you are editing them, and will let you see the full text (but in mark-down format, without any rendering). Me and @SioN wrote this solution in the other thread, but I wanted to summarize it.
And no, you cannot edit posts of other people.