I was wondering too...
我靠，这的人都不知道sth是something的缩写 － 你说这中国的英语教科书都谁编的呀？
that's exactly what happened to me
I don't think it is a bad habit to use acronym in email at all.
what is HX?
very good article to read about gold, oil, financial sector...
you didn't read thoroughly, did you? :)