Hide signature blocks by default
For example Mailbox app and many traditional *nix email clients have this really nice functionality that hides signature blocks after "-- " by default, which makes reading lengthy email threads much faster. However, you should be able to expand and read them if you wish.
That is many companies that nowadays choose use signatures which contain all possible ways to contact, disclaimers, advertisements, cat pictures etc. resulting in several paragraphs of noise and annoyance.