When using vim-pandoc, I'm having some funny behavior with headers:

For instance,

if I position the cursor on a word and press v-a-w and then <localleader> - i, I get italics.

if I position the cursor on a word and press v-a-w and then <localleader> - b, I get bold.

However, if I position the cursor on a word and press v-a-w and then <localleader> - #, I get No String Under Cursor.

Is this the wrong way to assign a block of text to a header?