Wiki pages and message board messages can have attachments. This files are stored outside of the document library.
When attachments are deleted from a wiki page or a message, they should be moved to the recycle bin so that they can be restored. However, these attachments in the recycle bin by themselves, outside of the context of the page or the message don't make much sense and can pollute the Site Recycle Bin too much. For this reason, there will be specific UIs inside a wiki page or a message to show the Recycle Bin only for elements in this page or this message. These attachments won't be shown in the Site Recycle Bin. (We will probably need to change the DB model a little bit to support this)
The Settings for enabling the Recycle Bin and the number of days for the clean up also apply to these entries.