Section "3.1 sed script overview" says:

> sed commands follow this syntax:
> [addr]X[options]
> X is a single-letter sed command. [addr] is an optional line address...

Considering that I've seen this misconception repeated in several places online, and considering that sed's POSIX specification is more clear on the matter ("[address[,address]]function [...] The function can be preceded by <blank> characters. These optional characters shall have no effect."), i suggest adding this piece of information to this section of the manual.

Thanks for your time.