To be clear, I'm talking in this case about double negatives originating in Japanese, not ones that are being translated into it.
When I was in college, one of my professors taught the class to use [疲]{つか}れていなくない in place of 疲れた, explaining it as a face-saving measure by at least putting up appearances of saying you're not tired. Is the resulting 〜なくない ending standard or valid? If so, is this practice at all common, or is was the professor passing on her own idiomatic usage? If it's relevant at all, said professor grew up in Osaka.
疲れた
. – istrasci Apr 1 '14 at 14:37