I had the same questions in my mind as I went to apply to airlines after my CFI expired, as I let in expire when I was in new hire training at my first airline in 2002. Since then I have always listed the CFI experience on my work history and also checked the boxes for instructor experience, but I have made no mention of the actual certificate nor do I list it under that section. It has never seemed to be a problem since I have been hired at three airlines since 2002, one regional, one major and one legacy. As always though, put what you feel is best on your applications, don't shortchange yourself, and be able to explain everything and you will be just fine.