SPECIAL PREMIERE: On Oct. 22, David Letterman went to Washington, D.C. as recipient of the 20^th annual Mark Twain Prize for American Humor. (To which I say: After 20 years, to not make room for the Smothers Brothers is just shy of criminal.) But in the past few days, a change was made to the program produced for PBS to honor and preserve that occasion. Sen. Al Franken participated in the event, but according to PBS, has been edited out of the broadcast after being accused of sexual harassment by a fellow USO tour member a decade ago. “Every year,” PBS said in a carefully worded statement, “this program is edited for both length and content to keep it focused on its intended purpose as a celebration of American humor.” Okay – but another question worth asking is, “What would Mark Twain want?” Check local listings.