Unsupported, use at your own risk.

negative-low-priority-urgency.patch

From e5db453a74b31e244871cd95005f65493d9f64d4 Mon Sep 17 00:00:00 2001
From: Tomas Babej <tomasbabej@gmail.com>
Date: Wed, 18 Mar 2015 16:37:34 +0100
Subject: [PATCH] Task: Make L priority negative

---
 src/Task.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Task.cpp b/src/Task.cpp
index edbc2166a9f85214bb69448b7a3e5a1409066114..3cf551d53d6884507589084442d573587e775871 100644
--- a/src/Task.cpp
+++ b/src/Task.cpp
@@ -1748,8 +1748,8 @@ float Task::urgency_priority () const
   const std::string& value = get_ref ("priority");
 
        if (value == "H") return 1.0;
-  else if (value == "M") return 0.65;
-  else if (value == "L") return 0.3;
+  else if (value == "M") return 0.5;
+  else if (value == "L") return -0.3;
 
   return 0.0;
 }
-- 
2.1.0

Well alright! This is something I've been looking for, and I understand the implications of adding an external patch, just don't know how to apply it.. does this come with clues? could it?