This is great, thanks @Cat! I actually like the added detail of the “onclick” event. Having the ability to opt-in first rather than having it happen automatically is always a plus.
There are two other open source embeddable chat systems I have seen used on Write.as - First is Utterances, a commenting system based on Github issues. Anyone who makes a comment needs a Github account (which is a deal breaker for some). Then there is Commento which has a “name your own price” model.
Another alternative is allowing your posts to be annotated on with Hypothesis, a free web annotation platform. It works by allowing someone to highlight parts of your post and make annotations through them. You do need an account to do this but it is free and allows you to annotate the rest of the web. I have it implemented on my blog and another Write.as user, @mikka has it on his. See it in action on one of Mikka’s posts here.
Hope that helps!