It is useful too as it is not censoring anyone where they would be unable to reply to your comments as is the case when using the on-site blocking. If you block someone on-site, that user cannot reply to any of your comments and nobody else has an opportunity to see what they have to say in reply to your post. With uBlock they can still post, it is just that whatever they post is hidden only for you. Blocking off-site via uBlock still permits them to freely say what they want, as they should be able to. However, them being free to say what they want doesn't mean what they say needs to be seen and read by all or that it is of any value or worth anyone's time to read. This is mainly why I went ~~almost~~ completely to using uBlock for blocking versus the on-site blocking - nobody gets censored and they don't get to waste any of my time or disrupt my attempts to keep informed on topics which I expect is the goal for many of them.