Less possible when you're getting hundreds of messages per day on all your online accounts with eg pictures of your children leaving school or your workplace.

No that actually sounds like a really good time to start ignoring things. You don't feed the trolls, real life or internet.

What's more inflammatory, ignoring a troll after he happens to find a picture of your children, or aggressively attacking their actions on their medium of choice? Don't feed the trolls.

Reddit do not officially have such a thing. The closest would be to use a browser equipped with the Reddit Enhancement Suite.

As in ignoring by not acknowledging the messages. This is not reddit specific, but for all sites. I can demonstrate on you right now.

what do you mean? is it like facebook's "hide all from X"?