Per the steam release, there is a hidden achievement. Looking at the global stats reveals it to be "Straight" and a picture of Catherine the bar tender in Whiterain, so I think she's the key to this
Viewing post in Secret ending
The translation string names include these so that seems promising 😯
"$Diag-AffinityCatherine_Ending-TextEntry-00",
"$Diag-AffinityCatherine_Ending-TextEntry-01",
"$Diag-AffinityCatherine_Ending-TextEntry-02",
"$Diag-AffinityCatherine_Ending-TextEntry-03",
"$Diag-AffinityCatherine_Ending-TextEntry-04",
"$Diag-AffinityCatherine_Ending-TextEntry-05",
"$Diag-AffinityCatherine_Ending-TextEntry-06",
"$Diag-AffinityCatherine_Ending-TextEntry-07",
"$Diag-AffinityCatherine_Ending-TextEntry-08",
"$Diag-AffinityCatherine_Ending-TextEntry-09",
"$Diag-AffinityCatherine_Ending-TextEntry-10",
"$Diag-AffinityCatherine_Ending-TextEntry-11",
"$Diag-AffinityCatherine_Ending-TextEntry-11-2",
"$Diag-AffinityCatherine_Ending-TextEntry-12",
"$Diag-AffinityCatherine_Ending-TextEntry-13",
"$Diag-AffinityCatherine_Ending-TextEntry-14",
"$Diag-AffinityCatherine_Ending-TextEntry-15",
seems fairly conclusive, though I have no idea how to drink at the tavern. I feel like i've tried clicking everywhere in there, no extra options to be straight when drinking the orientation swapping beer, and no way to enter not at night. Are there any beers we can take with us to the tavern? Does the shield above the fireplace mean anything?