According to the result of the discussion in my feature request, the packages are merged into one named "extras". The method names are adapted accordingly. And I created an additional package called "ast" containing higher level methods for the parser tree.

The look-ahead for whitespace characters in super- in subscripts was meant for an edge case. LaTeX-like notation `x^2 + x^3` leads to a senseless formatting `x<sup>2 + x</sup>3`. But the look-ahead had the side effect to fail perfectly normal Markdown like `H~2~O text`.

The look-ahead for whitespace characters in super- and subscripts is essential because a caret or a tilde may also be used for other markup or literally. The enabled extensions shouldn’t force a user to escape all existing literal characters or interfere with other markup. Edge cases may remain.

…new approach with less code duplication.

This is a preliminary version. The goal is to create one NodeKind "inlineTag" for all simple inline tags. But I am not sure if it’s going to work out, so I want to leave this on record.