[jabbernotty]

If a person says that something is a gem, they can be sincerely saying that they think it has positive value. Your interpretation was that the phrase was being used in a sarcastic manner. That may well have been the case here, but it doesn't have to be so.

[jufo]

I think the "half an hour" bit is significant. If someone complained that they tried to learn Prolog and gave up after half an hour they wouldn't get much sympathy from me.