Given the grammar:

https://github.com/textmate/markdown.tmbundle/blob/master/Syntaxes/Markdown.tmLanguage it seems that vscode can't properly handle the construct https://github.com/textmate/markdown.tmbundle/blob/master/Syntaxes/Markdown.tmLanguage#L105

i.e.: when parsing a markdown with '##' with this construct (markup.heading.${1/(#)(#)?(#)?(#)?(#)?(#)?/${6:?6:${5:?5:${4:?4:${3:?3:${2:?2:1}}}}}/}.markdown), it'd be expected that the result is markup.heading.2.markdown, whereas vscode is just giving markup.heading.${1/(#)(#)?(#)?(#)?(#)?(#)?/${6:?6:${5:?5:${4:?4:${3:?3:${2:?2:1}}}}}/}.markdown as the result.