I'll give an approximate explanation, although you can find a complete answer by searching the source code for the variable
$g_disable_condescending_comments, which is what gets changed when you alter the prejudice options. (There is also Native code that uses this variable.)
The reason the menu option is called "prejudice" instead of "sexism" is that I initially intended for it to also affect other forms of bias (such as the prejudice against common-born PCs and companions from elements in the nobility), but supporting that is pretty low on the list of possible tweaks.
Duh said:
I have seen it in dialogs.py, so its definetely influencing the way things are worded and i am rather sure that it also changes what consequences are avaiable (f.e. does a lord duel with a female player).
Yes, things like: Will a king invite the player to join the kingdom without the player asking? Will a king offer the player a fief? Will lords make comments about how women shouldn't be leading soldiers? etc.
Also, in Native, Martial and Upstanding lords will always reject a female player character's courtship, because a warlord doesn't match their ideal of femininity. Altering the prejudice setting removes that.
(As a side note, I altered the game to allow factions to be patriarchal/matriarchal/gender-equal on a kingdom-by-kingdom basis. Since Diplomacy doesn't alter the setting there isn't any difference here for the standard NPC kingdoms, but if the player forms a new kingdom it is considered egalitarian. Based on some of Matheld's dialogue I had initially considered marking Nordic culture as gender-equal culture, but decided to leave that to individual players to keep or change.)
Ringwraith #5 said:
And what exactly is the difference between the "default" and "high" settings of sexism?
Even on Default, I toned down the "Martial/Upstanding lords refuse the player's advances" thing so the absolute prohibition doesn't apply to all of them. On High, the behavior is the same as Native.
Aside from that, setting the prejudice level to "high" means that subaltern-gender lords (both the player character and NPCs) will be treated by some characters as if their renown were less than it actually is. It also might influence some dialogue options.