The Cyrillic script is described by Wikipedia as follows:
The Cyrillic script /sɪˈrɪlɪk/ is a writing system used for various alphabets across Eurasia (particularity in Eastern Europe, the Caucasus, Central Asia, and North Asia)… It is the basis of alphabets used in various languages, especially those of Orthodox Slavic origin, and non-Slavic languages influenced by Russian. As of 2011, around 252 million people in Eurasia use it as the official alphabet for their national languages, with Russia accounting for about half of them. With the accession of Bulgaria to the European Union on 1 January 2007, Cyrillic became the third official script of the European Union, following the Latin and Greek.
Bulgarian accounts suspended
Bulgaria is among the countries using the Cyrillic script. It seems that twitter has been suspending Bulgarian accounts and filtering out their messages from conversations merely because they are posting using the Cyrillic script. It appears from user experience that mentioning @YouTube or any other major account using the Cyrillic script can create trouble.
Even if the initial tweeter is unaffected if someone replies using Cyrillic script they have an even larger chance of being suspended. Some of the users suspended have had accounts as far back as 2009 and others have many thousands of followers. The suspensions no doubt extend well beyond the Bulgarian community.
Denitsa Hristova’s tweet illustrates what happens.
Russians a target of suspensions
Michael Tracey tweets that according to Twitter’s criteria a user is regarded as having links to the Russian government if he or she frequently tweets in Russian ie. using the Cyrillic script.
The most likely explanation as to why this is happening is that Twitter has strengthened its algorithms for weeding out Russian bots. Since Russians use the Cyrillic alphabet just the use of the Cyrillic script is a red flag. This would explain why the Bulgarians were getting suspended. This is much too broad a filter. Obviously, many Russians are not trolls.
Users can recover their accounts
Although users are able to recover their account fairly quickly after being suspended, even after this Twitter can still treat them unfairly and discriminate against them. When they respond to a message thread they often get “tweet unavailable” messages and are muted from sending notifications to others. This sort of treatment is called “shadow banning”. If the user complains to Twitter support they are told that their account isn’t banned so things are fine even though they are not. Twitter appears to be unresponsive or slow in responding to complaints.