Visit ucomment.me and use Search bar to find people by their username. Click '+Follow' on a user page to subscribe.

After this time, your comment will be deleted. Set default lifetime for your comments in settings lifetime Lifetime can be set explicitly when you leave a new comment

Can be either public or followers-only. Set default privacy for your comments in settings privacy Privacy can be set explicitly when you leave a new comment

By default, your profile is opened for subscribing to you. Close profile allows to you control list of user, which subscribing on your new publications, and your comments with privacy mark 'Followers'.