Ability to mark any post as unread

[alefattorini (Alessio Fattorini)]

I like it and asked before

Keep posts unread

Sometimes I read posts from my mobile but can’t reply immediately but I postponed them since the reply is too long or simply I have no time. Can I have a button to keep posts (not entire topic) unread? Right now I’m using bookmarks but it’s not really handy. Do I have other options?