Why can I down-vote some comments but not others?

Question

On certain HN posts, I can up-vote and down-vote comments. Then on other comments in the same post, I can only up-vote (there is no down-vote arrow). Why?Screenshot:https://share.getcloudapp.com/Z4uj8w2l

verdverm · Accepted Answer

Looks like they are too old?You can't downvote replies and the reply feature is disabled after a certain amount of time, as well as when it is

Why can I down-vote some comments but not others?

On certain HN posts, I can up-vote and down-vote comments. Then on other comments in the same post, I can only up-vote (there is no down-vote arrow). Why?
Screenshot:
https://share.getcloudapp.com/Z4uj8w2l

Looks like they are too old?
You can't downvote replies and the reply feature is disabled after a certain amount of time, as well as when it is <1m old (under some circumstances?)

Why can I down-vote some comments but not others?

On certain HN posts, I can up-vote and down-vote comments. Then on other comments in the same post, I can only up-vote (there is no down-vote arrow). Why?Screenshot:https://share.getcloudapp.com/Z4uj8w2l

Looks like they are too old?You can't downvote replies and the reply feature is disabled after a certain amount of time, as well as when it is <1m old (under some circumstances?)

On certain HN posts, I can up-vote and down-vote comments. Then on other comments in the same post, I can only up-vote (there is no down-vote arrow). Why?
Screenshot:
https://share.getcloudapp.com/Z4uj8w2l

Looks like they are too old?
You can't downvote replies and the reply feature is disabled after a certain amount of time, as well as when it is <1m old (under some circumstances?)