I want to add that my mother's grandfather and 2 uncles who were lawyers were of Scottish heritage, but it was way back there. The original ancestor came to America in the 1700s. I don't know if that has anything to do with it, but "pled" has always sounded right to me. Using "pleaded" sounds ignorant to me. Besides, we have "bleed-bled," "feed-fed," and "read-read" (the last sounding like "red").

I totally agree that the use of "pled" sounds correct, while using "pleaded" sounds babyish to me. Example;
The defendant pled guilty.
The newspapers and online news reports lately seem to always be using pleaded; I don't know when they changed. My mother was always a stickler for grammar and she would have used "pled." She had 2 uncles and a grandfather who were lawyers, so I wonder if she picked up "pled" from them.