Inorder to embed YouTube's live chat in an iframe, there is a formula one is supposed to follow when constructing the link.

Basically it's     
<iframe src="https://www.youtube.com/live_chat?v=VIDEO_ID&embed_domain=DOMAN_NAME"></iframe>

Just replace VIDEO_ID with the video id, and DOMAN_NAME with the root domain name.  Simple enough.
The problem arises with the & symbol.  When IPS switches from source mode to wsiwyg mode it replaces the & symbol with

&amp; 

so then going back into source mode to look at the original iframe you see

<iframe src="https://www.youtube.com/live_chat?v=VIDEO_ID&amp;embed_domain=DOMAN_NAME"></iframe>

Which makes the chat not load.  Does anyone know a way around this?
Or better yet, has anyone successfully embedded a YouTube live chat on their forum?

 

Have you tried creating a custom button for it through the ACP?