no. non-transitiveness through local naming, the reason this has not
allowed serious damage in current practice.
a receiving operator could limit scope, if they chose. something like
route-map foo p 10
match community blackhole
match as-path ^([0-9]+_){1,2}$
set ip next-hop null0
route-map foo d 20
match community blackhole
route-map foo ...
yes, they *could* if they so chose.
the problem is that most won't. as we know, unintentional (or more
correctly, thoughtless) leakage of all sorts of garbage is rampant
today. weaponizing (you gotta love american verbing of nouns)
well-known communities that will assuredly be leaked; what could
possibly go wrong?
randy