VTCompose\Markdown: The performance of the parser is likely not optimal
The performance of the parser should be benchmarked, the bottlenecks identified and the implementation fixed.
There is a chance that one of the problems is the recursive parsing of nested blocks. The JavaScript CommonMark reference implementation uses a different approach which identifies all nested blocks the first time an input line is read. It should be considered to rewrite the block parsing to follow the same approach.