As ssh has the -n option for this (and therefor I'd treat this as a documentation enhancement), it should be clearly stated in the manual page that even a "ssh <host> true" will eat stdin. This is especially not obvious here (bash script):

echo -e "1\n2\n3" | while read s; do echo Hello; done

vs.

echo -e "1\n2\n3" | while read s; do ssh <host> echo Hello; done

Please, add this to documentation - it'd have saved me some time ;)

Kind regards
Eckard