If a user searches "Other users" within his "personal tools" with the help of "user attributes" (e.g. with last name), he can't confirm the search with the Return/Enter-key. Within the "Members Management" of a course or a group, it works fine.
Adversely there is no different screen if the search has no findings or when the search has not been started yet. so people sometime guess not to find s.o. but in real haven't searched yet.