SAN FRANCISCO, April 15 (Xinhua) — Twitter, Inc. on Friday announced that its Board of Directors has unanimously adopted a limited duration shareholder rights plan following an unsolicited, non-binding proposal to acquire Twitter by Tesla CEO Elon Musk. The Rights Plan, often called the "poison pill", will reduce the likelihood that any entity, person or group gains control of Twitter through open market accumulation without paying all shareholders an appropriate control premium or without providing the board sufficient time to make informed judgments and take actions that are in the best interests of shareholders, according to the announcement. The Rights…