Some applications have never heard of ES_DISABLENOSCROLL and attempt
to force scrollbars to be always shown (with ShowScrollBar() or
similar) when otherwise richedit would hide them. If richedit attempts
to wrestle control back, a recursive loop of requests can result if
app overrides WM_SIZE behavior. Apparently native never reads the
scrollbar state, and operates from some sort of internal state, so
that scrollbars can be modified externally without native trying to
wrestle back control. This is confirmed by attached tests. An
exception: EM_SCROLL will restore visibility to a scrollbar that was
forcibly hidden.