Legally it could be argued that a user using a fake name is fraudulently using the platform contrary to their terms and conditions. It is good that Poloniex recognized it as an issue and was sensible with the solution they offered. However - others may go down a different path and report it to the authorities in the jurisdiction that they are in.
Allowing a user to change their name on the platform potentially could cause liability for the platform if it is done by a hacker that then drains the funds of a user. Phishing was less of an issue years ago. Currently phishing and compromised user accounts are a huge threat.
The reality is that this situation would not have occurred if the user had not lied about their personal details. It is the user that committed the legal wrong
.How to find out whether the user's data are right or wrong? Is the wish to find it out by starting a KYC-check is enough ground to make a decision that funds are illegal and to withhold the funds?
How do you think, what procedural steps have been taken by the exchange to have a reason to call each particular case "criminal" and to block users funds?
By your logic, can Tradesatoshi consider itself both investigation authority and judicial authority? They started mandatory KYC-checks without reasons and blocked users funds without any evidence for uncertain time, simply because they themselves started the KYC-checks. Seems, they don't need any of those authorities to decide what is legal and what is not.
For example, Binance blocks accounts suspected of committing a crime for 3 days. In the absence of official documents on the beginning of the investigation after these 3 days, the blocking is removed.
By the way, many exchanges do not request user data at all until verification is required - only login and password. Binance, which is mentioned above, is one of them. Because there is no sense to ask for such data until KYC.