I'm never sure what that word "engineer" in the Dilbert strip actually means, since it's an American usage. Here in the UK, an engineer is somebody who does things like studying the structural streses in suspension bridges, which is clearly not what is meant here.
But if "engineer" in the US is a synonym for "programmer", I'm a retired programmer so how I think is by definition how a programmer/engineer thinks - if not necessarily how *all* programmers think.
Ok, lets think this a bit like engineers*, shall we?
Be true to yourself = be yourself
You = True
You = You
The affirmation while not incorrect, doesnÂ´t add any value to the original variable, ergo, doesnÂ´t means anything.
In another, slighty more defined context:
PHB = bag of hot air = Nothing of value
Nothing = Nothing, 0=0, 0=True to 0?
The advice doesnÂ´t means anything because nothing has nothing to be true to.
*Well, at least that' s how engineers think in my head
Dilbert says it literally means nothing because everyone is always true to himself (herself) all the time. Even for people who seem to conform to the expectations of others, behaving out of their normal character for the sake of making a good impression or just for conformity - even these people are being true to their own nature specifically because being a conformist IS their nature.
That's why Dilbert says PHB's advice literally means nothing.
And he's quite correct, at least from this perspective.