SAN FRANCISCO : Twitter on Thursday restored the ability to block unwanted followers from peering at posts, quickly reversing a policy change that triggered a barrage of criticism. “Earlier today, we made a change to the way the ‘block’ function of Twitter works,” Twitter’s Michael Sippey said in a blog post late Thursday in California. “We have decided to revert the change after receiving feedback from many users - we never want to introduce features at the cost of users feeling less safe. Any blocks you had previously instituted are still in effect.”