The len godoc uses a blockquote to list the rules for its semantics.
The item that describes channels is a bit long, so it's split in two
lines. However, the first line ends with a semicolon, and the second
line can be read as a sentence of its own, so it's easy to misinterpret
that the two lines are separate.
Making that easy mistake would lead to an incorrect understanding of
len:
if v is nil, len(v) is zero.
This could lead us to think that len(nil) is valid and should return
zero. When in fact, that statement only applies to nil channels.
To make this less ambiguous, add a bit of indentation to the follow-up
line, to align with the channel body. If lists are added to godoc in the
future via #7873, perhaps this text can be simplified.