This setting automatically added the `-status:deleted` metatag to all searches. This meant deleted posts were filtered out at the database level, rather than at the html level. This way searches wouldn't have less-than-full pages. The cost was that searches were slower, mainly because post counts weren't cached. Normally when you search for a tag, we can get the post count from the tags table. If the search is actually like `touhou -status:deleted`, then we don't know the count and we have to calculate it on demand. This option is being removed because it did the opposite of what people thought it did. People thought it made deleted posts visible, when actually it made them more hidden.
Helpers
This directory contains helper functions used by views. Helpers are used for simple common functions, such as linking to users or formatting timestamps.
Helper functions are globals. If you see an unnamespaced function in a view, and it's not a Rails function, then it's probably a helper defined here.
All helper functions defined in this directory are globally available to all views. They're not limited to single views. For example, the functions in posts_helper.rb are available to all views, not just to app/views/posts.
The use of helper functions should be minimized. Partials or components are preferred for more complex widgets, or for things used in only one or two places. Helper functions should be limited to very simple things used in nearly all views.