This would ensure transparency in conversations, says Twitter
Twitter says that while the hide button would give users control over their conversations, the secondary option to view hidden tweets would ensure that the main capability isn't exploited.
Essentially, there will be an element of transparency between the original tweeter and audience, which would prevent people from hiding their own inappropriate/hate comments or silencing dissenting opinions, like those of people commenting against politicians.
No word on global launch yet
Having said that, you should understand that this capability is only being tested in the US, Japan, and Canada at this stage.
Canadians have given a positive response to the feature, noting that it helped them hide abusive or irrelevant tweets. But, the capability still remains experimental, and there is no word on when or if it will hit other regions.