I can read Chinese but can not type Chinese. So here is my comment about the above paragraph.
1) The Chinese investment money bought 房利美和房地美's bonds not stock.
2) The reason they buy because two bonds pay higher interests. For example, a recent 5-year bond pays 4.1% comparing 5-year US Treasury notes of 3.01%. 1% difference means 1 billon profit for every 100 billion investment.
3) As long as 房利美和房地美 are not default and the investment is held through maturity, the investment is safe.
4) When companies are filing bankruptcy, stock holder will get nothing. Bond holders will be paid depending on the remaining values. This is the risk. However, Uncle Sam will not allow their bankruptcy to happen. As you already knew, Uncle Sam is helping these two companies now.
5) Right now, the Bond's King, the Pimco's Bill Gross is actually saying the bonds for these two companies are undervalued.