Humorous or not humorous? It's sometimes a matter of context. For me, Spock's delivery of "Only Nixon could go to China" was exactly as humorous, in the context of TUC, as "they are not the hell your whales" was in the context of TVH.
Besides, it could have been a Vulcan proverb, expressing something not as easily expressed in plain language (or at least plain Vulcanian). Why not have a proverb from Earth history if no equivalent event in your own planet's history had quite the same flavor?
As for the remark about "Shapespeare in the original Klingon," that's different, in that everyone present would know Shakespeare was an Earther. Clearly intended, therefore, as a joke.
Besides, it could have been a Vulcan proverb, expressing something not as easily expressed in plain language (or at least plain Vulcanian). Why not have a proverb from Earth history if no equivalent event in your own planet's history had quite the same flavor?
As for the remark about "Shapespeare in the original Klingon," that's different, in that everyone present would know Shakespeare was an Earther. Clearly intended, therefore, as a joke.