What is the oldest age individual that you feel comfortable chatting with online? What is the youngest?

I know the general rule for dating a younger person is half your age plus 7 years. But what about chatting? And the oldest?

For me, the youngest is probably around 35 yo if it's flirty chat...and about 60 to 65 for the oldest (I'm 56). For platonic chat, I'd say any age might do.