You should fix the name of the TOOLBAR_DrawDDFlatSeparator function and the comments above it if you think it should be called as a result of the CCS_VERT window style and not the BTNS_DROPDOWN button style.
I've been thinking about that. Yes, it's 100% that separators change orientation on CCS_VERT, and not on BTNS_DROPDOWN (this style affects only the button/separator flow). I'll rename that function and resend the patch.
-- Igor