I believe in any other shell that uses the pipeline syntax fish inherits, it is allowed to break the statement at the pipe itself. That is, if echo foo | cat - | cat is valid syntax, so is:

echo foo |
cat - |  # Tab space comments.
cat

foo

But in fish, the newline must be escaped:

Expected a command, but instead found end of the statement
echo foo |
          ^

Seems... buggish.