I don't know why it take so long for Telligent to fix this bug as well as why it wasn't fixed in SP1.
But anyway, we made a quick fix for it
Technical details:
There are 2 reasons for this bug or actually 2 bugs with cumulative effect :)
1. Incorrect processing of user names with spaces (like "c r i s", which system translate to "c-r-i-s") and dashes (like "c-r-i-s", which system translate to "c_2D00_r_2D00_i_2D00_s"). This need to be addressed in Web\Utility\FooterFragments\Core\UserInfoPopup.ascx. An example how it should be treated see in hot fix.
2. Incorrect Ajax method in web service CommunityServer.Web.Utility.FooterFragments.Core.UserInfoPopupAjax, which get user details based on userProfileUrlPattern (see 1'st reason). When we call Users.GetUser(Globals.UrlDecodePathComponent(username)) we actually ignore the fact, that user name might have space characters. In a fix we created UserInfoPopuAjax inherited from CommunityServer.Web.Utility.FooterFragments.Core.UserInfoPopupAjax with GetUserInfoByUsername method which takes care about spaces in username directly.