If you open someone's profile page other than yourself, for example, Chris Osiak:
If open your own profile page:
Why does it mention positive changes for others' profile?
Because if their recent reputation changes are only negative rep changes, then the summary won't be shown at all. You can still see all public negative rep changes on their "reputation" tab though.
After downvote (after waiting until the caching breaks): reputation is decreased by 2, no change on the summary.
On "Reputation" tab: the downvote is still shown correctly
After upvote (after waiting until the caching breaks): reputation is increased by 5, the summary is shown with recent reputation changes.