I personally find it really annoying when the whole page slides over as the community chat is opened. The way it's presented makes it look like an overlay UI element, but when it slides the page over it just becomes confusing and makes the page look worse overall.
The community chat
Hmmmm.. I disagree.
It used to act as an overlay ui element, and I personally found that extremely annoying. The chat would simply block the page and i'd have to close it. Mind you, I still wanted to chat, it was just covering too much.
The majority of the time you're on the SH site, you will probably want to talk in the Community Chat. So, it makes sense for the div to not be in the way constantly.
It only slides over if your screen doesn't have enough space to show all of the content, and having the chat block things on the page objectively makes the ux worse. I don't really see how the page sliding over could be considered confusing. I agree that it does look odd, but that's what you're stuck with if you don't have enough screen space to see it as intended.
maybe you should invest in a properly sized monitor?
As for the forum, the chat is really just shoehorned in right now. It uses a global sidebar widget, so that's why it looks awkward. I will probably work on getting it moved up into the corner like on the main website right now at some point. I think that will also make it not reload every time you click on a new page. But it was much easier to just set it up in an iframe in the sidebar when I set the forum up, so that's why it's there as it is now