The default set of stop words used by the Lucene analyzer in Alfresco causes these common words to be dropped from the search index. Unfortunately this causes a search for the 'will' in any list of users to return zero results. This behaviour seems to be particular to more recent versions of Lucene.
The default set of stop words is perhaps useful for indexing free text but for indexing more structured information (and user information in particular) it is of little benefit and causes items that should be returned in search results to not get returned. A more permissive indexing strategy would be helpful for these properties.