The immediate inspiration came from the title of an e-mail from Jon Jantsch's Duct Tape Marketing: Can Handwritten Letters Get You More Clients, referring to a post by Nick Gibson at Six Revisions.
However, a few days ago I'd read a couple of articles about typography for lawyers. There is even a website titled just that, by Matthew Butterick, a font designer turned lawyer, I kid thee not.
Between those two, a realization struck me immediately (well, almost; I was a bit low on caffeine, which I'm remedying right now):
Ekhm, ignore handwriting for now, through I'm positively sure — and without needing to see any tangible proof to boot — that it would get you more clients or 'better' ones.
Rather, before we even look that far, there are still printed letters.
See, on your website and in PDF brochures you're limited by whatever fonts the reader has, not you.
Depending on who you work for, that may be less of a problem — I've once seen a web designer use Caslon of all things, because his readers could mostly be presumed to already have it on their systems anyway (it's an Adobe font that comes with Photoshop). Similarly, most institutional clients probably have MS Office, so most of them would see them if you defined them in the CSS sheet, perhaps with Georgia, Palatino or even Times as a fallback from among the sixteen or so mostly stable set of (relatively) 'web-safe fonts'. (For server-side hosting, embedding fonts in PDFs and other forms of what effectively is font distrubution you'd need a suitable licence from the copyright owner.)
But, on paper, your options are not limited in that way. You have more control. Paper is paper, it doesn't matter what type of hardware or software platform the reader runs. What's best, once printed, it always stays the way it is, for everyone.
Naturally, the visual impression is not the same for everyone, but that's something for you to figure out. The point is, you can do a lot in terms of advanced typography on paper these days, even with the same old MS Office (well, not too old, say: 2013) that everybody else has and to some extent possibly even in Open/Libre Office.
Tracking, leading, kerning, ligatures, widows and orphans and off-black shades, different fonts for headers than for the main body of the document, you name it, it's there. You can also hand-pick just the right paper and envelope and not skimp on the ink or toner since you're probably going to be printing just one or two pages.
You can make it look very, very good, without at the same time making it look over the top — although striking the right balance may, naturally, require some practice and will always be at least a little on the subjective side, just like font pairing (google it).
Of course, use a fountain pen for signatures and any handwritten additions (depending on your demographic, it may be more courteous to write greetings and salutations in hand, and the courtesy might not be lost on the recipient).
Naturally, this is even more important for anyone who does certified translation or anything else that requires hard copy.
What else? Years ago e-mail was exceptional because it was hi-tech. These days, however, paper mail is already exceptional — and thus both special and upscale — in many corporate environments. It's something to put your hands on, to touch, to tear your eyes off of the monitor screen and read like in old times.
Some clients may find it superfluous or pretentious, or both, but others will perceive it as a welcome sign of reliability, seriousness, permanence, stable foundation, a sign that you aren't going to disappear overnight like an e-scammer. Sort of like what still having landline came to mean, at least before the fake kind became popular.