Oh yes, and a solution which would tackle the both problems, would be just to glue the preposition and the noun together, i.e. making an expression. I think that would help also to the thing Malte mentioned (which is, to be honest, about the same problem we're having).
E.g. "Join Class" = "Ilmoittaudu kurssille", when
"Class" alone would be just "Kurssi". Now these messages with just one word like "Class" are used in many totally different meanings.
My proposal:
Let's use one word messages just when the words are truly alone on the page, and in other cases, put the whole expression in the message. And at least let's not use same messages like class_pretty_plural (just invented the name) in different contexts:
Classes in "Total 15 classes" != Classes in "Join classes"
