Almost nobody cares about anything other than ad blocking and to top it off the reply to the comment you linked is even mentioning that they were only talking about ad block...
I think you don't understand the difference between an extension (for which manifest version matters) and an intrinsic feature (for which the manifest means nothing). It's either that, or you want to convince people that FF the only way. No, it isn't. Deal with it.
https://news.ycombinator.com/item?id=43349506