In other words: good reasons to avoid using "Ph.D" and other titles appended to your email.
From an article on the New York Times about the latest Spider-Man movie (the one filmed by Marc Webb):
Gwen Stacy asks Peter Parker if he likes branzino: you know, “Like, the fish?”.
Then she invites him to dinner, where everyone is saying “branzino”: Denis Leary (playing Gwen’s dad), Peter, Gwen again. We see a full branzino at the dinner table, neatly plated.
Why branzino? The film never says — it just offers up this delightful serving of unexpected weirdness.
In the comments, a guy who does not forget to specify his title writes:
Branzino is a New England cold water fish that is usually thrown out, but many restaurants and people interested in ecology believe its use may be a viable way to help reduce the destruction to cod, flounder and other more popular North Atlantic fish whose numbers [and size] are dwindling. There is a belief this will also be a long term benefit to the smaller family fishing economy in the N.E. It was in all probability an ecology statement....and Dennis Leary is a true New Englander.
David M. Klein, Ph.D. South Florida
I am all for avoiding internet anonimity because it causes all sort of animal behaviour (see any internet forum debating politics or canon vs nikon merits or iphone vs android).
But to specify to the world that you are a friggin Ph.D like if it gives more credit to your ideas, this I cannot stand.
I see this so often in work emails -- and that's bad enough, but if you use it also when commenting some innocuous sentence about branzino (which is by the way not New England specific as I have been raised with branzino or spigola, and I'm from Bari, Puglia) then you just sound like a pretentious dick.