Stand to be corrected but not aware of ever being IM's in Canada. MM's disappeared in the early '80's and OM's in the early '90's. I remember a bit of a fuss when the MM's were being withdrawn. This happened a few years after most ILS DH's being lowered from 300' to 200' in this country. The fuss was associated with some of the older generation flight directors (FD 108? comes to mind) that utilized a feature G/S EXT, glideslope extension, that was triggered by the MM flashing that "dampened" (things are bit fuzzy of the specifics) the F/D cues when going through 300' AGL. Things could get a bit aggressive otherwise.
To answer your original query though......no markers .....nill effect on ILS function.