Not sure I agree with this. My startup (Frogmetrics, YC S07) hasn't tried to sound big or small. Our site focuses on the service we provide, in concrete language with a clean design. We don't try to sound bigger than we are, but we also don't play up our smallness with a bunch of cute catchphrases either. We've been pretty successful so far at getting big customers, and I think we'd have done less well with a more "startup authentic" aesthetic.
I think the better lesson is to tailor your messaging to your target buyer. If you're selling to a level III coder at a big company, put the message in a form (s)he will like.
"tailor your messaging to your target buyer" -- I think this is the key insight here!
Personally, I like the approach of avoiding allusions to size on your main site, using the expected language of your customer, and not trying to hide it in your personal communications. It's OK if the company blog unveils how tiny you are, anyone looking there is already interested beyond your size.
I think the better lesson is to tailor your messaging to your target buyer. If you're selling to a level III coder at a big company, put the message in a form (s)he will like.