Looks like ^S only starts torrents stopped manually with ^D.
Torrents stopped for other reasons (ratio limit and hash
mismatch in the cases I witnessed) don't react to ^S.
^D^S worked with ratio limit and absolutely nothing with
hash mismatch (earlier version from Lenny would retrieve
damaged portions and resume seeding after a rehash, which
is probably the right thing to do.)

Also, the Lenny version would automatically set Ignore
Commands on manually restarted torrents previously stopped
on ratio limit. 8.5 doesn't. Probably has to do with changes
in ratio handling.