Good question.

Isn't the inability to apply the loop hint to a right join a bit bizarre though? Although it seems pretty obvious why this happens, there is in fact something odd about the exclusion of right join. After all

A right join B on A.x=B.x

is identical in meaning to

B left join A on A.x=B.x

and I can apply a loop hint to the second. So I ought to be able to apply it to the first, unless the optimiser interprets the loop hint as saying "use a nested loop join where the outinner loop is on the right hand component of the join, that is the table which occurs second in the text of the query" rather than just "use a nested loop join (choosing whichever component the optimiser thinks best for the outer loop)". The optimiser has great freedom generally, and making the loop hint specify more of a constraint on the optimiser than it really needs is out of tune with that usual freedom.

edit: "outer" should be "inner", see text struck and replaced above