A bug in Markdown parser for ~?

In GitHub issues in preview, when I type:

~~A B C ~5 D E F~~

it doesn’t work as expected to me.

I expect: A B C ~5 D E F, but instead I get ~~A B C ~5 D E F~~.

I know, I can probably use ≈ in many cases (like A B C ≈5 D E F), but it is harder to type quickly, and still I think it is a bug in markdown parser on github.