That was the toned down version :p
I just don’t see strikethrough as ‘big’ or controversial enough to omit from the core standard. There is already a de facto standard for it, and lots of existing markdown that uses it. It seems as if there is a feeling that not adding something to the spec is always easier than adding it, but what I’m trying to say is that sometimes poor decisions made early on can cost a lot more further along in the project’s lifetime.
As a user, when I google for ‘markdown strikethrough’ and find something that seems to suggest that two tildes will delete text, then try to use it and it fails, it really frustrates me. I am suggesting that you should try to channel that kind of antipathy towards specific markdown implementations for failing to conform to the spec, rather than towards CommonMark for failing to conform to people’s expectations.