Background:

Once I faced a situation in which I saw in my activity feed that one of my friends received a rare achievement in a difficult game that we both played sometimes. I wanted to congratulate him for completing that hard challenge, but have not found any feature to do so. I have sent a request to Steam support team, and one of the members advised me to share my idea here.

The idea:

My suggestion is simple. I think it would be great to let users make comments in activity feed, below achievement unlocks of their friends or the profiles they are subscribed to. Surely, if this idea comes to realization, I guess that there will be a privacy setting to restrict such comments if you do not want to receive them.

Reasons:

I think that Steam will benefit from improving user-to-user interaction that is focused on gaming activity, and users will benefit from sharing the joy of unlocking achievements and praising each other for such activity.

I will be waiting for your support and additions to my idea.