What Does it Mean When You Block Someone on YouTube?by David Nield
If another YouTube user is posting comments or sending you messages that are persistently inflammatory or abusive, the site enables you to block him. Blocking another user on YouTube prevents him from commenting on your videos and your channel, and from messaging you through YouTube. Users are blocked and unblocked using the button on their profile pages.
How to Block
To block another on YouTube, open her profile page by clicking her username on any comment, for example. Click the username link and open the "Connect with" drop-down menu and select "Block User" from the list, then "OK" on the confirmation page. The blocked user is then prevented from subscribing to your channel, commenting on your channel, commenting on your videos and sending you messages through YouTube. The same menu can be used to unblock a user.
Viewing Blocked Users
To see a list of users you've blocked on YouTube, click the arrow by your avatar picture to open the user account drop-down menu. Select "YouTube Settings" and then "Inbox" and "Address Book." Click "Blocked Users" to see the list. Users can be unblocked from this page by selecting the username and choosing "Unblock" from the list of options that appears. You can still comment on videos by and send messages to users you've blocked.
When to Block Users
You can block other YouTube users as and when you choose. Members who abuse the messaging or commenting system on a regular basis can be blocked -- for example, as can anyone who posts the same negative or unhelpful comments on your videos time and time again. The user in question doesn't receive a direct notification of the block, but he will no longer be able to access comment boxes for your videos or the send message option.
Moderating comments is a useful way of preventing other members from leaving negative, abusive and unhelpful posts on your video pages. To turn comment moderation on, visit your video channel and choose the "Info and Settings" option from the Edit drop-down menu by the clip in question. Choose "Advanced Settings" and then tick the "Allow Comments" box, selecting "Approved" from the drop-down menu next to it. Comments will then only appear when you approve them from your YouTube inbox.