Accidental double posts are normally dealt with without much problems, I don't see the need of having that mod installed.
Mainly, because I think it would bring also one disadvantage. The place where one is more likely to see "double-posting" is in Storywriting, where people writes their stories, commonly in form of chapters, so each post is a chapter. That ain't fitting to the definition of "harmful double-posting" but the script to merge all "double-posts" made by same user into one would not notice the difference, unless it has an option for it to act only in certain forum areas, or a slight code modification has to be applied to it to not convert, let's say, a story made by several post of the same user, occupying 1 page and a half, into one single post that, would not only turn out being a "page" longer than what someone might assume as logical, but also be impossible to read as it would be an impressive text column.
Double posting is, then, being dealt correctly as it is now, and since I personally see that flaw to an "automatic" double-posting avoidance, I'd prefer things to stay the way they are.