Consider this case.
The official street name is 'Grafton ST'. (This example is for Charlottetown, Prince Edward Island, Canada.) The word "street" is, in the official record, and on the street sign, abbreviated and capitalized.
Note as well that the 'official' Canada Post address database, all addresses in the whole country follow the style of abbreviating "Street" to "ST", "Avenue" to "AV", and so on. Canada Post: "Street type should be placed after the street name in abbreviated format (see Table 1: Street types for a complete list of common abbreviations.)" link
The list of Canada Post abbreviations for street types is here.
The name in OSM is currently "Grafton Street". Is it not logical for OSM to match the official name exactly, and change it to "Grafton ST"? Do you still object to having "Street" as "ST", if that's what the official record is, and if that's what the street sign says?