Hong Kong stocks, which joined a regional rally in the morning, erased earlier gains and ended Thursday lower, as some investors took advantage of the morning rebound to dump shares. The Hang Seng index ended the session down 0.2 percent, at 23,728.07, while the China Enterprises Index lost 0.4 percent, to 10,246.89 points. But falls in sectors including property and telecom dragged the indexes lower, reflecting how fragile investor confidence is, after a roughly 8 percent gain so far this year.