A question about road courtesy...

My commute goes by the quarry in Owasso, so I've been on the road
with a lot of big trucks. Generally, these drivers are courteous
and safety conscious. They see me nearly every day.

145th Street is just 2 lanes. Many of you know it from doing the
Monday night ride.

I've been signaling when a big truck passes and it's back end
clears my bike. I signal just as if I were making a right turn,
holding my right arm out horizontally. Some truck drivers
respond by flipping on their right turn signal and coming back
over into the lane. Is this a good practice?

I ask because this morning I received an e-mail from someone here
at work, describing my actions exactly. Apparently there was a
car behind one of these trucks, and it appeared to the driver
that I was signaling for a right turn without ever turning. I've
never been too concerned about that, because there's seldom a
place to MAKE a right turn when I do this. Still, given a
choice, I'd rather have a confused motorist than a confused
tractor-trailer driver.

(....and yes, I'm probably going to get wet on the way home
today! Oh the joy.)