You’re welcome @nibl!
So this is where that little bit of JavaScript comes in handy to grab the slug of the post, because once the subscribe form is submitted, it redirects to the top of the post with the message that you subscribed. It should work now though.
It should because that detection happens server side. I don’t know why it isn’t working here.
But I think it’s best to build a solution for this @nibl than having to do this work around, because there are some things that we cannot replicate with the custom JS that help reduce spam subscriptions.
I’ll bump the post signatures topic in the meantime and see what people think about the feature as a whole. Once we have a better idea of the demand we can look into it further.