I know that the double posting (usually of comments, but other things too) has been a thorn in everyone's side. Well, not everyone. I think it's mostly folks on mobile devices - especially iOS devices 'cause Safari encourages double clicking of links to make them work. Well, it's been driving me batty as well. The good news is that I think (this time I'm a bit more confident) that I have a solution and it'll be released with Smaug. yay!
So I was doing some searching on what's causing the problem and I found this post: https://www.drupal.org/node/107358. It's pretty hilarious. The participants spend an awful lot of posts "proving" the issue. As it turns out it's a function of clicking the submit button after the server has received the comment but before it returns a response. Something that's a common occurance when we're using cell data rather than wi-fi (which is where I tend to test things so I hadn't been able to duplicate it). Thankfully, my development server is slow slow slow so after reading how to duplicate I did so.
Then I found a really slick module that disables the submit button for a couple of seconds (I'll need to play with it to get the right amount of time) so that the server can return a response and thus double posts will be eliminated. How cool is that?
Anyway, I'm always trying to get stuff working better for you and if you run into any issues at all or have something you'd like to see on the site then by all means, please drop me a note at email@example.com and I'll take a look at it. I aim to please, after all.