My bad, paragraph border is what the "\n______\n" gets replaced with, while they are hyphens, not underscores, in your question. The "\n------\n" is not auto-replaced in my (too old?) OO.
So another guess: try style:text-underline-style or similar in linked documentation (probably it's "Underlining" in Character Style in GUI, you are looking for).
In reply to Re^3: Horizontal Line By OODoc
by vr
in thread Horizontal Line By OODoc
by sachss
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