A simple script to insert the tags could look like this:
tell application id "DNtp"
repeat with theRecord in (selection as list)
if type of theRecord is markdown then
set theText to plain text of theRecord
set theTags to ""
set theTagList to tags of theRecord
if (count of theTagList) is greater than 0 then
repeat with theTag in theTagList
if theTags is not "" then set theTags to theTags & ", "
set theTags to theTags & "#" & theTag
end repeat
set theText to "tag: " & theTags & return & return & theText
set plain text of theRecord to theText
end if
end if
end repeat
end tell