The last seen was useful for deciding whether to comment to old answers. Before if I saw an old an old answer to a question and wanted to leave a comment asking for clarification, I could look at when the user was last seen to get an idea as to how likely the user was to reply to my comment and how long I might need to wait for a response. I mean if the user had for instance been last seen that day I could more reasonably expect a response than if the user had been last seen 3 years ago and leaving a comment would be more likely to be worth it in the former than in the latter. Now if I see an answer to an old question and am confused about something the user says in the answer I'm less motivated to comment asking for clarity as its harder to know if my comment will actually be worth it.

The 'Last seen' was useful for deciding whether to comment on old answers. Before if I saw an old answer to a question and wanted to leave a comment asking for clarification, I could look at when the user was last seen to get an idea as to how likely the user was to reply to my comment and how long I might need to wait for a response. I mean if the user had for instance been last seen that day I could more reasonably expect a response than if the user had been last seen 3 years ago and leaving a comment would be more likely to be worth it in the former than in the latter. Now if I see an answer to an old question and am confused about something the user says in the answer I'm less motivated to comment asking for clarity as its harder to know if my comment will actually be worth it.