Etiquette when pinging patches?

[Richard Sandiford]

I don't want to waste everyone's time with protocol, but I was wondering:
what's the etiquette when pinging patches?  Should the ping be a reply
to the original message (i.e. should it be in the same thread), or should
it be a new thread?  I was once asked to use new threads instead of the
old one, so that's what I've been doing, but there have been two cases
recently in which people responded to the original message after the new
thread developed.

Richard