In ODATA-933 we allowed using instance annotations in $filter. In doing so we ended up treating annotations as a path segment, matching the path syntax.
Although perhaps perfectly aligned with the path syntax it looks weird to have two separators, both / and @ sign separating the property to which the annotation applies to and the annotation itself. Everywhere else where we, in our JSON payloads, have an annotation, we use property@annotation.
I'd propose we'd amend the resolution of ODATA-933 accordingly and omit the / from the reference to the annotation and therefore address an annotation value on a property as
NavigationPropertyName@Term#Qualifier instead.