Read receipts, typing and last seen

In Settings › Privacy & Security, you control whether people can see:

• Read receipts, the second tick that says you have read a message.
• Typing, the sign that you are writing.
• Last seen and online.

These work both ways. If you turn off read receipts, you stop seeing other people's as well. That is deliberate, so the setting cannot be used to watch people one-sidedly.

You can also choose who sees your profile photo and your about text: everyone, only people you have a chat with, or nobody.