With the clever quote feature introduced in phpBB 3.2, the quoted text includes the username, which displays as a link to the user's profile. 

Now consider the case where someone's username has been changed. There might some confusion when the old username is displayed in the quoted text, but clicking on the link takes the viewer to what appears to be another profile, because the username is now different. 

I realize that for backwards compatibility the clever quote feature must retain the username that existed at the time of quote and there would be processing overhead to check every clever quote to ensure that an username change hasn't occurred, but nevertheless the implementation does allow for the possibility to create confusion in the mind of anyone who clicks through on the link under the quoted username.