Here's a simple one that I like.
Define these vars in your definitions script:
lastLine=lastLine or ""
lineBefore=lineBefore or ""
Then make a new trigger and name it LAST LINE TRIGGER, or wutever
regex trigger:
(^[A-Z].*)
block:
if matches[2]==lastLine then
selectCurrentLine()
deleteLine()
cecho("<maroon>+<reset>")
end
lineBefore=lastLine
lastLine=matches[2]
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Now anytime you get a duplicate line from the mud, it will be deleted, and a maroon + will appear at the end of the preceeding line. Also now you can access the var lineBefore in your scripts which can be handy.