There's a list of global diplomacy modifiers. A while back I hypothesized that these modifiers are your reputation and played a game based on that hypothesis; it seems to hold up although I suspect there's more involved than just that. This is from the descr_faction_standing.txt file:
Code:
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; DISHONEST TRANSGRESSIONS ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;------------------------------------------
Trigger 0075_DT_Stole_Back_Settlement
    WhenToTest Transgression

    Condition TransgressionName = TC_STOLE_BACK_SETTLEMENT

    FactionStanding global -1.0

;------------------------------------------
Trigger 0076_DT_Bribed_Away_Settlement
    WhenToTest Transgression

    Condition TransgressionName = TC_BRIBED_AWAY_SETTLEMENT

    FactionStanding global -0.15

;------------------------------------------
Trigger 0077_DT_Nullified_Alliance
    WhenToTest Transgression

    Condition TransgressionName = TC_NULLIFIED_ALLIANCE

    FactionStanding global -0.1

;------------------------------------------
Trigger 0078_DT_BROKE_TREATY_TERMS
    WhenToTest Transgression

    Condition TransgressionName = TC_BROKE_TREATY_TERMS

    FactionStanding global -0.15

;------------------------------------------
Trigger 0078b_DT_Break_Alliance_War
    WhenToTest Transgression

    Condition TransgressionName = TC_BROKE_ALLIANCE
        and DiplomaticStanceFactions = AtWar

    FactionStanding global -0.5

;------------------------------------------
Trigger 0078c_DT_Break_Alliance_Neutral
    WhenToTest Transgression

    Condition TransgressionName = TC_BROKE_ALLIANCE
        and DiplomaticStanceFactions = Neutral

    FactionStanding global -0.1
Code:
;------------------------------------------
Trigger 0099_prisoners_released_increase_global
    WhenToTest FactionLeaderPrisonersRansomedCaptor

    Condition RansomType release
          and NumCapturedSoldiers > 80

    FactionStanding global 0.02
;------------------------------------------
Trigger 0100_prisoners_executed_decrease_global
    WhenToTest FactionLeaderPrisonersRansomedCaptor

    Condition RansomType execute
          and NumCapturedSoldiers > 80

    FactionStanding global -0.02

;------------------------------------------
Trigger 0101_sack_settlement_decrease_global
    WhenToTest SackSettlement

    FactionStanding global -0.02

;------------------------------------------
Trigger 0102_extermination_decrease_global
    WhenToTest ExterminatePopulation

    FactionStanding global -0.05

;------------------------------------------
Trigger 0103_occupy_settlement_increase_global
    WhenToTest OccupySettlement

    FactionStanding global 0.02
For the majority of the game I played, just going by this raised my reputation up from mixed to reliable, to very reliable and to trustworthy. About this point was where I installed the patch, and within the next 5 turns the three alliances I had (HRE, Byzantium, and the English) had all been betrayed. It looked like I took reputation hits even though they were the ones who broke the alliance, although they took much bigger hits. My reputation dropped from trustworthy down through very reliable to reliable over the course of the next 50 turns. Admittedly, I did execute a few prisoners and sack one city in the course of that time, but either the hits are bigger the later the date or you get a much bigger modifier for actions you don't normally take. Nothing I could do has been able to bring it back up since, in fact it dropped to mixed before I just gave up on it entirely.