Closing unclosed tags is invalid and problematic

What is explicitly handled by snarkdown -https://github.com/developit/snarkdown/blob/b01a5cddabd9fba97175c896e14c881e586a4631/test/index.js#L155 is incorrect and might cause trouble for consumers

https://babelmark.github.io/?text=*foo

Start by reading test/index.js around line 155 and compare snarkdown's handling of the cited *foo input with the linked Babelmark result. Determine the expected behavior for the unclosed tag case, then add or update a focused test so the chosen handling is documented and reproducible.

Written by the indexing model from the issue text.