Specifically, if you specify a display name of [benpa] then that will cause the contains_display_name to match against the regex (^|\W)[benpa](\W|$), which matches any event with the word "a" in it.

This is because we pass the display name straight into _glob_matches and the glob to regex conversion doesn't escape regex characters in the glob. (We also probably don't want to be using display name as a glob)