The 32-year-old, who frequently uses Twitter to say nice things about Moore, admitted he loves online flirting in an essay he wrote for the January issue of US Harper's Bazaar.
He said: 'Sending sweet nothings on Twitter or Facebook is also fun.
'In some ways, it's no different than sending flowers to the office - you are declaring your love for everyone to see. Who doesn't like to be publicly adored?'
Although Ashton warned that you sometimes have to be cautious about what you post.
Kutcher, who titled his essay 'Has Texting Killed Romance?', said: 'Just remember that what you post is out there and there's some stuff you can't unsee.'
But the Killers star added that online affection won't replace good old real-life gestures.
He said: 'When someone needs us, he or she needs all of us, there's no text that can replace a loving touch when someone we love is hurting.'