there is a simple way to avoid any and all double posting...
instead of simply clicking the "New Post" button, right click it and choose "Open in new tab" (assuming your browsers supports that, which as far as I know, ALL the current Linux Browsers do)
When the new tab opens, enter your post and click the post button.
Now switch back to the original tab and refresh the page, you WILL see your new post, and then you can simply close the tab where you entered it.
I ALWAYS use this method of posting, and I NEVER have any double posts, because I know if it posted or not (it always DOES post, but doesn't always show the new post unless you refresh)
And assuming that under some rare circumstance. you go back to the original tab and refresh and your new post ISN'T there, well the new tab you opened should still be open, and you can try again, without having to re-type anything... (although I have never had that happen in all my posts)