Interesting idea. But I wonder how often a level up of any kind occurs? And do you have to log in on "the day" to see it? ("The day" might be within 24hours of the level up.)
Extending this (to a probably bad extreme): keeping track of level ups seen by each user such that if there are gone for a week, there might be a few all at once. (And if they're gone for a year, it might be a tidal wave.) Then we'd need "friends" and "acquaintances", and we'd only be notified of their changes. Geez, now it sounds like FB or something. Never mind =)
-QM
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Quantum Mechanics: The dreams stuff is made of