It really depends who you are leaving out and why. My husband says withholding information that I think is important is lying by omission and I would agree most of the time but I don't think everyone would always see a problem, especially with regards to not telling you what they are texting about. You also have confidentiality and respect of others to consider, sometimes it's kinder to say nothing.

I keep somethings to my self as people judge me and stop talking to me