Who said: "if people understand what you are saying, it probably isn't
worth saying."

Oscar Wilde wrote several epigrams with similar themes.

Intentions by Oscar Wilde 2
http://www.classicbookshelf.com/library/oscar_wilde/intentions/2/

"I am but too conscious of the fact that we are born in an age when
only the dull are treated seriously, and I live in terror of not being
misunderstood."

Phrases and Philosophies for the Use of the Young by Oscar Wilde
http://www.angelfire.com/blues/zahidhomepage/phrases.htm

"If one tells the truth, one is sure, sooner or later, to be found
out."

"A truth ceases to be true when more than one person believes in it."

"Only the great masters of style ever succeed in being obscure."

hlabadie-ga