I just found a number of references to this in the "Pled versus Pleaded" thread.

Apparently it is a pet peeve for a number of people.

WRT DAW's dissertations:-

If spoken they would certainly be classified as verbal diarrhoea.

Is there a term for the written equivalent?

If one applies the logic:-
signage = Signs collectively, esp. commercial signs or those on public display; the design and arrangement of these
to some other -age words then would the following be true:-
dotage = arrangement of dots
garbage = design of garb
pillage = collection of pills

Advantage Hairy.
JJMB to serve.

The antipodeans do seem to come with some rather idiosyncratic word usage.
Perhaps a result of being so far removed from civilised influences.

@campobello
It is more like downgrading than evolution and there is nothing neat about it.
Just another sorry example of how acceptance of erroneous usage is leading to debasement and dumbing down of the language.