Twitter has rejected anonymous communication, saying that it gives priority to tracking trolls rather than protecting dissidents.

For instance, Twitter blocked Magnus Hedemark's account because he used it through Tor.

The article suggests that this includes blocking access to his old tweets.

This is one reason why you should never cite a tweet by means of a link to twitter.com. Proper practice is to copy it directly into your article, like any other quotation.

An additional reason for this is so that Twitter does not get information about who reads these quotes and the article where you cite them.

Twitter says it blocks the accounts because their postings look like spam. But if you're willing to consider blocking an account, surely you could first try some less abrupt response that would teach the user about the perceived problem.