No longer able to create an AVD pool - SQL truncation error

Question

So, I just went to create an AVD pool in my MSDN/dev tenant. Same way I always do, and received an immediate error. This was whether I created virtual machines at the same time or not.

Error was:

{
    "status": "Failed",
    "error": {
        "code": "1",
        "target": "ArmBaseExceptionFilter.OnException",
        "message": "UnknownError",
        "details": [
            {
                "code": "MTBrokerDBException",
                "target": "MultiTenantBrokerDatabase",
                "message": "SQL Exception: error: 2628 and message: String or binary data would be truncated in table 'rdinfra.dbo.EndpointPools', column 'LastModifiedBy'. Truncated value: 'me_mycompany#EXT#@mycompany.onmicros'.\r\nThe statement has been terminated."
            },
            {
                "code": "DbUpdateException",
                "target": "Microsoft.EntityFrameworkCore.Relational",
                "message": "An error occurred while updating the entries. See the inner exception for details."
            },
            {
                "code": "SqlException",
                "target": "Core Microsoft SqlClient Data Provider",
                "message": "String or binary data would be truncated in table 'rdinfra.dbo.EndpointPools', column 'LastModifiedBy'. Truncated value: 'me_mycompany#EXT#@mycompany.onmicros'.\r\nThe statement has been terminated."
            }
        ]
    }
}

The obfuscated value runs to 69 characters normally and it's being truncated at 64. Again, this has never been a problem before. What changed? I can't easily change my name, nor my company's.