Even with an interpretation ‘it must be operational’, the absence of a subject or operational consideration in the MEL is not approval for absence of operational thought.
Too often, IMHO, pilots revert to a simplistic ‘SOP’ / ‘legal’ interpretation of documents without thinking about the issue. Of course thinking requires some basic knowledge of the subject, which unfortunately is often absent or has been biased by inappropriate speculation.
So from the gist of the discussion above, when / how would single reverse be used?
Personally I would not; and to avoid the ‘but if you really had too’ argument, there are few if any such situations which could not be covered by a pre departure decision. No go for crosswind on a 'dry' take off (RTO) – the Captain judges the value, and a 'dry' crosswind or wet/ contaminated runway for landing (EU operators may, in addition have to consider landing distance if reverse is credited on contaminated runways).
The MEL covers pre departure issues; what if there was an en route failure, is there similar operational advice in the QRH or is the issue entirely ‘operational’?