Here's a userscript (for Greasemonkey / Tampermonkey / etc) that I wrote up for it:
http://pastebin.com/nbFDWQzUPluses/minuses:
+ It technically does let you chat, even showing the appropriate Lichess spectator box. It does this by looking at the game ID through the analysis button.
+ Looks decent, I suppose, considering how little screen real estate is left on the Lichess TV page.
+ It will tell you if
@thibault changes things to break it and more-or-less deactivate itself. I think.
+ I left in my comments and silly tries so you can laugh at me and see how doing anything better than this is slightly tedious.
- Only works in the minimum board size, sorry. I really did try.
- Loads two Lichess pages so uses more bandwidth. Sad, but it's the only way I could think of doing it without using a third party chat service.
- Since obviously not everyone will have this, you might not find too many people to chat with.
- Scrolls down the page when it loads the chat box, which is mildly annoying. I would make it scroll back up but that might be *more* annoying.
- Only tested on Chrome, but I don't see why it wouldn't work with other browsers.
- You might find it untrustworthy since it's a userscript on pastebin. I mean, it's safe and doesn't share any data or anything, but if you can't (or don't want to) read through it, you only have my word for that.