Lets back up and use an analogy. Domestic abuse (aptly put I'd say). A man beats his wife, but only occasionally and when he has been drinking. He drinks in private though, so the wife has no way of knowing when he will become combative. The wife then begins to have a pervasive, long lasting fear over time that greatly affects the way she speaks and how she does things.
You are basically saying that it's the wife who creates the fear, not the abuser, and not only that, but you are saying the wife isn't in any more danger from washing the dishes than she is from talking to the husband about drinking, which I think is obviously false.
You then proceed to make some very strange logical leaps:
" Edward Snowden has done an interview with John Oliver, which presumably means everyone visiting any site hosting that interview is also on a permanent NSA watchlist."
No I don't think anyone has said that but you. An attempt at a straw man perhaps?
"Yet despite apparently almost everyone everywhere being under constant surveillance by the NSA at this point, there appears to be no global chilling effect"
You have provided no evidence to back up this claim, while there is plenty of evidence to support otherwise. For example, a recent high profile suit against the US by Noam Chomsky, Chris Hedges, Daniel Ellsberg, and others.
"Don't let ... [this] cause you to act with more caution than necessary."
I would agree with this, as FDR said, "the only thing we have to fear is fear itself". That doesn't remove the fact that the chilling effect is real, is growing, and still affects people though, so stop pretending otherwise.