Apparent bots

[Shirai]

Any particular reason for that, I wonder? Because it doesn't sound like it makes a lot of sense... They happily cite server issues when asked about, for example, inventory expansion, but then they continue to store characters of perma-banned accounts? Sounds kinda illogical to me?

By deleting those accounts or characters they also delete data they might need in the future in case a SE wants to pursue legal charges against a company/party, or vice versa.

As a side effect, they can't make new characters with that name to harass you with. Making it safe to remove them from the list forever.

Apart from that, character data is merely that, game data.
And data isn't the issue when they talk about the issues you mention, it's server load, the traffic that takes place between the client (you) and the servers.