It works the same as the "attempt to block outside search engine" settings -- we obey the preferences of the location of the comment. If you disable global search on your journal, comments on your journal (no matter who they're by) won't be publicly searchable.

The same goes for other accounts. If a community or journal disables global searching of their account, then content there (including comments) will not be publicly searchable. If they have chosen to let their account be indexed, though, then we will index the content on their accounts.

To manage your search related settings, please visit the Privacy tab of the Manage Account page.