I am sure it is obvious what he means by "read". Its a tell to gauge how scummy a person might be. You, more often than not, read on the lowest part of that gauge. The "Town" part. Because, to Town, everyone is supposed to seem somewhat scummy at least, you stand out like a mountain in Florida.
Appearing Too Townie: There's no official name for this one, but being too concerned about your image; specifically avoiding things that might be seen as scumtells. The idea is that scum are very concerned about being found out, and so want to act nonscummy. Townies know they're not scum, so they're less concerned about LOOKING nonscummy and more concerned about finding scum.
I take personal credit for poorly naming this one. Do note that the tell regards concern with appearance, especially at the cost of effectiveness, not merely towniness.
Appearing too towny is not, by itself, a scumtell, because there really isn't a point at which someone's so townlike they must be scum. There is, however, a point at which they're so
concerned with appearing townlike that they might be scum.
A decent analogy might be to assume you're attempting to catch liars amongst honest people. There is no point at which someone's so honest they're actually a liar, but there is a point at which they're doing so much to
look honest that they're probably a liar in disguise, not a genuinely honest person who wants everyone to know about it.
if I remember correctly, once is a coincidence, twice is suspicious, but, today making the third time, three times is a pattern.
Do note that this is a very loose, often incorrect rule of thumb; it should not be applied to complex situations without proper reasoning. It also involves issues of WIFOM.
This isn't Sherlock Holmes, and we don't have all the time in the world. Right now, having a possible reason and a possible theory is better than having nothing at all.
While you can never be absolutely certain of anything, it is important to ensure that your best guess is indeed your best guess, not merely a possibility you've decided to run with.