Changing sub-wiki type leads to loss of user participation prior to change

[kastashov]

1. User makes edits to pages in a single course sub-wiki;
2. Lecturer changes the setting to "Single subwiki per every user".
3. User makes further page edits in their own sub-wiki.
4. On the "Participation by user" page, only changes made on step 3 are displayed, but not changes made on step 1.

Is it possible to display user participation for all subwikis? Is it as simple as amending the SQL query in ouwiki_get_user_participation(), or are there possible considerations that make this change more complicated than it seems?