Several users have a double-posting problem

I see here various ways to try to solve this issue (and other issues too):

1. Disable the mailing lists.

2. Do item 1, and improve the forums and issue trackers so as to allow simple plain-text notifications, like: "Topic [Topic name] has the following new comment: [Comment]", this would allow the recipient to keep the e-mails as bookmarks in their email inbox so as to remeber them that they'll need to visit the relevant topic to answer that comment, or simply delete the received email notification if he really doesn't want to remember to answer that comment.

3. Do 1 and 2, and find the reason as to why the JavaScript in our website makes most browsers freeze... But this freezing issue is secondary, we don't need to focus on that for now.

I find that I only double post when my browser takes longer to load after saving the comment.

Double posting occurs for me when I skip the Preview step and post directly:
https://trisquel.info/en/forum/duplication-forum-messages