Lily's Protection

[danajsparks.livejournal.com]

When Lily Potter died, the magic of her sacrifice gave her son protection against Lord Voldemort. When Voldemort tried to kill Harry with an Avada Kedavra, a spell for which there is no known magical shield, Lily's protection caused the spell to rebound and hit Voldemort instead. More than ten years later, when Prof. Quirrell, possessed by Voldemort, tried to touch Harry, Lily's protection caused his skin to burn. Clearly, then, Lily's protection was both powerful and enduring.

I have a couple questions, though, about Lily's protection....

1. If Lily's protection made it impossible for Quirrellmort to even touch Harry, then why didn't it prevent a fragment of Voldemort's soul from latching onto Harry?

2. Likewise, why didn't Lily's protection appear to have any effect upon the diary horcrux, even though Harry touched it and entered its pensieved memories?