Post a screenshot from the public chat?

Can I post an excerpt from a chat history from a Twitch stream on my page?

It's a testimony from a person that was made in the chat a few years ago. The stream was recorded and is now available as a video for everyone on the platform. I now take a small screenshot of the public chat and post it on my page (also accessible to everyone)

Am I allowed to do so legally, even if people think that they are in a bad light there? Or do I have to ask permission first from every person whose username you can see?

You don't have to ask someone's permission if it happened in a public chat that is open to everyone.