`* 2.` does not produce <li>2.</li> about knitr

[atusy]

This behavior comes from Pandoc which parses * 2. as a bullet list containing an ordered list.

» echo '* 2.' | pandoc -t native                                                                                                                                                
[ BulletList
    [ [ OrderedList ( 2 , Decimal , Period ) [ [] ] ] ]
]

You need backslash escape to avoid the behavior.

» echo '* 2\.' | pandoc -t native                                                                                                                                                
[ BulletList
    [ [ OrderedList ( 2 , Decimal , Period ) [ [] ] ] ]
]

Just for the next time you face unexpected behaviors with markdown syntax, I would recommend inspect Pandoc's behavior.
knitr only deals with chunks and inline chunks, not with markdown syntaxes in general.