The use frequency of the character yin appears very low incommonspeech and only appears as morpheme in the words.
“引”在现代汉语普通话里使用频率很低,而且只作为语素出现在词语里。
2
The idea of recommending humor in a presentation gets a bad rap because of the common and tired practice of opening up a speech with a joke, almost always a lame one.
By "difficult," it is meant, I think, well, first of all that it is in some sense set apart from commonspeech, as a specialized and highly self-conscious use of language.