bbPress.org

But then, the code in this post is fine:

WordPress Header on bbpress

Maybe the previous one was edited and that’s where the trouble started?

My post had GT LT replacement too, I had to edit it and remove the php tags… but this is not a solution, because there are post in which you cannot remove the tags, as https://bbpress.org/forums/topic/internet-explorer-problem-1?replies=8#post-69386