Once 'load_anon_lastread' is enabled the L_SEARCH_UNREAD and L_SEARCH_NEW options should be displayed too.
"Search new posts" should require login
L_SEARCH_NEW should not be shown, because that uses $user->data['user_lastvisit'] which is user based and makes not so much sense for the guest user. With L_SEARCH_UNREAD I however agree.
dmitry_n, the way user_lastvisit being handled now is not ideal and perhaps will be changed, but I doubt we'll go this way for 3.0.x.
The subsilver2 part doesn't look so nice. We might want to leave it as it is in subsilver2.
Fix is verified
I definitely not understand why "Enable search for unread posts" option has been added. "Enable topic marking for guests" is quite enough. Or is it supposed to be entire separate option? What for?
"Enable search for unread posts" has been added because the queries that are run to generate the page are quite expensive, which can be an issue on large boards. Thus, there should be an option to disable the new feature completely.
By the way, you started a discussion in the wrong ticket. This ticket is not about adding the "Enable search for unread posts" switch.