These 2 indexes optimise performance on profile pages.
The summary page displays:
1. A list of "Top Link" - links sorted by number of clicks posted by user
2. A list of "Top Replies" - replies made by a user that go the most hearts
These two areas could devolve into full index or table scans, new indexes are there to avoid this cost on large dbs
One minor downside is that storage requirements go a tiny bit up to maintain the new indexes
Sam