As mentioned, allowing users to easily change usernames (let's call it "display name" to disambiguate) makes it easier for users to dodge the consequences of harrass or scam other users. If your site has a social aspect, maybe consider whether bans, blocks, chat histories and the like between users will carry through a username switch.

Another point to consider is anonymity or privacy concerns. It's fairly frequent that someone makes an account with their real name and then posts something they regret and wishes their real name to no longer be publicly visible. Sometimes this is because they were caught bullying or the like, but is often for legitimate reasons as well like over-sharing personal details of their life. This recent question comes to mind as an example:

I accidentally entered password for a website as a username for another website

In this case, submitting a service ticket to be reviewed by a human sounds like a reasonable approach.

As mentioned, allowing users to easily change usernames (let's call it "display name" to disambiguate) makes it easier for users to dodge the consequences of harassing or scamming other users. If your site has a social aspect, maybe consider whether bans, blocks, reports, chat histories, etc will carry through a username switch (ie will a user be aware that they are talking to the same account, even though the name has changed?).

Another point to consider is anonymity or privacy concerns. It's fairly frequent that someone makes an account with their real name and then for whatever reason regrets attaching their real identity to it. Sometimes this is because they were caught bullying, but is often for legitimate reasons as well like over-sharing personal details of their life, or they become the victim of bullying. This recent question comes to mind as a different example:

I accidentally entered password for a website as a username for another website

In this case, submitting a service ticket to be reviewed by a human or allowing a limited number of account name changes sound like reasonable approaches.

As mentioned, allowing users to easily change usernames (let's call it "display name" to disambiguate) makes it easier for users to dodge the consequences of harrass or scam other users. If your site has a social aspect, maybe consider whether bans, blocks, chat histories and the like between users will carry through a username switch.

Another point to consider is anonymity. It's fairly frequent that someone makes an account with their real name and then posts something they regret and wishes to remove their real name from being publicly visible on the account. Sometimes this is because they were caught bullying or the like, but is often for legitimate reasons as well like over-sharing personal details of their life. This recent question comes to mind as an example:

I accidentally entered password for a website as a username for another website

In this case, submitting a service ticket to be reviewed by a human sounds like a reasonable approach.

As mentioned, allowing users to easily change usernames (let's call it "display name" to disambiguate) makes it easier for users to dodge the consequences of harrass or scam other users. If your site has a social aspect, maybe consider whether bans, blocks, chat histories and the like between users will carry through a username switch.

Another point to consider is anonymity or privacy concerns. It's fairly frequent that someone makes an account with their real name and then posts something they regret and wishes their real name to no longer be publicly visible. Sometimes this is because they were caught bullying or the like, but is often for legitimate reasons as well like over-sharing personal details of their life. This recent question comes to mind as an example:

I accidentally entered password for a website as a username for another website

In this case, submitting a service ticket to be reviewed by a human sounds like a reasonable approach.