When Marky is fed an HTML fragment that includes the & (ampersand) char, it will choke/stop processing.
While testing my @workflowhq workflow [Emulate Drafts Web Capture Keeping Links][1], I noticed that if the clipboard has an "&" char, the MMD output I get is truncated there. Further testing validated that if the html fragment that is fed to Marky via the "HTML" option (http://heckyesmarkdown.com/go/?html={fragment}&read=1&md=1) contains an ampersand processing stops there.