Sometimes when you ban someone for harassment, they make alts and further harass you. Because IP bans are sketchy at best, the next best solution is shadowbans.

From the harasser's perspective, nothing has changed. They don't know that they've been blocked, and can comment/interact with your content as usual.
From your perspective, however, it's the same as a normal ban. You won't see their comments, DM's, etc.

This gets to the root of the issue by removing the harasser's anger and annoyance. I really think it would be good as an option, and fairly easy to implement.