Underline Titles (Markdown, reStructuredText) in BBEdit

gistfile1.scpt

-- Thanks to hristopher Stone
tell application "BBEdit"
	set textDocument1 to a reference to text of text document 1
	tell textDocument1
		tell line (startLine of selection)
			if startLine > 1 then
				set lineContent to contents
				if (length of lineContent = 1) and (lineContent is not " ") then
					set prevLineContent to contents of textDocument1's line ((startLine) - 1)
					tell application "BBEdit" to replace "." using lineContent searchingString prevLineContent options {search mode:grep}
					set its contents to result
					select insertion point after it
				end if
			end if
		end tell
	end tell
end tell