@techee I just reread you objection again and I think you misunderstood what `SCI_CHOOSECARETX` does.
From https://scintilla.org/ScintillaDoc.html#SCI_CHOOSECARETX (emphasis mine):
SCI_CHOOSECARETX Scintilla remembers the x value of the last position horizontally moved to explicitly by the user and this value is then used when moving vertically such as by using the up and down keys. This message sets the **current x position of the caret** as the remembered value.