It's been one of the great conundrums of Twitter in recent times, particularly during the presidency of Donald Trump. While, as many have noted, some of Trump's tweets clearly violate the platform's rules on hate speech, Twitter has opted to leave them up on the site.
For example this:
North Korean Leader Kim Jong Un just stated that the “Nuclear Button is on his desk at all times.” Will someone from his depleted and food starved regime please inform him that I too have a Nuclear Button, but it is a much bigger & more powerful one than his, and my Button works!
— Donald J. Trump (@realDonaldTrump) January 3, 2018
Would appear to be a fairly clear violation of this element of Twitter's rules:

Yet, despite this - and there are many other examples like it, from Trump and other high profile users - Twitter has opted not to remove it, or penalize the respective account. Why? Because they serve the public interest, because people have a right to know and discuss what the President, and other high-profile users, have said.
But that also puts Twitter in a difficult position - if these users can say things like this, why can't you or I, and what's the threshold for a 'public figure' anyway? Does this mean that verified accounts are held to a different standard than everyone else?
Twitter CEO Jack Dorsey has struggled to explain this stance, noting, at various times, the importance of hearing explanations direct from our leaders, that banning Trump is 'a Liberal fantasy', and more recently, suggesting that Trump is no worse than Obama in his Twitter usage.
But it remains a contentious point, the differing rule books for regular and famous users angers and confuses many. And Twitter's still looking to do something about it.
Speaking at the Technology 202 Live event this week, Twitter’s head of legal and policy Vijaya Gadde explained that they are investigating a new option which would enable the platform to label tweets which are in violation of Twitter's rules, but have been left up on the platform because they serve a particular purpose.
Gadde noted that the current system is confusing because it means that such tweets can “live on Twitter, and people can see it and they just assume that is the type of content or behavior that’s allowed by our rules". A labeling system would help to clarify which tweets are exempt, and could help to alleviate frustration, and lessen anti-social behavior.
But it still means that Twitter has to make concessions in its rules for certain actions. Case in point - last September, Twitter banned controversial broadcaster Alex Jones for violating the company's abusive behavior policies. The delineation between what someone like Jones has said, and what the President has shared, opens the platform up to accusations of bias, which is something that various far-right commentators, in particular, have claimed Twitter and other social platforms are guilty of.
If the rules are not clear cut, it's very difficult for Twitter to defend itself against such - yet, if Twitter can't ban anyone, then it's a free for all, where anyone can threaten and target anyone else, without recourse.
Logically, it makes sense for Twitter to keep certain tweets up on its platform - hosting Trump's in-the-moment thoughts, for example, is no doubt bringing more people to the site. But it's a very difficult balance. A labelling system for such may provide more clarity, but it likely won't resolve the problem.
Really, the only solution is for Twitter to uphold its rules for all users - but would it be willing to do so if it could potentially lessen its relevance in the broader media landscape? Does the need to serve the public interest work for Twitter, the business, or Twitter the utility?
Even with specific labels, there still seems to be more discussion required to resolve this key point.