In some of my post I didn't experience the long loading I don't know if the issue is already fixed but you could easily avoid the double posting for sure, after experiencing the issue, most of the button seems to be okay, preview button seems to be working fine and then if you already posted the topic editing it seems to be completely fine I didn't encounter any issue editing only if I click the post button I encounter the long loading.
After testing it I already understand how you could avoid getting the double post.
My post is taking too long to post and then I'm going to get the error It's just taking too long, my internet seems to be okay and fast so for sure, there are some issues.
It didn't show me my post as posted in the thread so I ended up posting my topic 2 times because of the issue so I just delete the 2nd one, browsing some topics seems to be okay and fast as well but I would just encounter the issue when I started to post.
Edited:
It seems to load for a long time without confirming that the post is posted but actually, if your going to check your post history your going to see that the post is already posted. so there are a lot of posts here in the forum that get double because after clicking the button they just don't know that the post is already posted so they ended up clicking the post button again or refreshing and clicking the post again.
Didnt encounter some of the issues it seems to be okay even though the preview is working completely, and editing seems to be okay as well, it doesnt seem to be a big problem because it is just the loading part that annoys me.
So if you click the post button already it seems like it was taking too long to load but the post seems to be posted fine, if your going to visit your recent post your going to see that the post is posted, so the tendency is you see the long loading some of the members probably think that it is still not posted but it is already posted, then they are going to refresh the page because of the loading then repost the topic so it always get double.