video insertion not possible in the network when not admin

Further Tom Eagles message, I reopen this question.
https://premium.wpmudev.org/forums/topic/video-youtube-or-another-insertion-in-post#

Only admin can put video (youtube, dailymotion...) in a post.
A non-admin member put the iframe code in HTLM mode, then whem he publishes the post the code disappears.
Nothing in the post.

Have you a solution ?

Note : WP version 3.7, all plugins updated

Thanks a lot