An answer to Interesting examples of vacuous / void entities was written, and only edited by, @JonasLinssen:

However, the answer shows up as having been written by @PrudiiArca:

The text "PrudiiArca" is a link to https://mathoverflow.net/users/129445, which is indeed @JonasLinssen's page.

Presumably this is because the user changed their name, which, as I understand it, is a totally normal and reasonable use of the software. However, shouldn't the displayed name of the post's author also change?

The post Failure to update changed username on (edited, community wiki) answer describes related behaviour, but the answer by @JohnOmielan indicates that this behaviour should not be observable in posts made after 2009. As you can see in the screenshots above, the answer in question was posted on July 8, 2021.

An answer to Interesting examples of vacuous / void entities was written, and only edited by, @JonasLinssen:

However, the answer shows up as having been written by @PrudiiArca:

The text "PrudiiArca" is a link to https://mathoverflow.net/users/129445, which is indeed @JonasLinssen's page.

Presumably this is because the user changed their name, which, as I understand it, is a totally normal and reasonable use of the software. However, shouldn't the displayed name of the post's author also change?

The post Failure to update changed username on (edited, community wiki) answer describes related behaviour, but the answer by @JohnOmielan indicates that this behaviour should not be observable in posts made after 2011. As you can see in the screenshots above, the answer in question was posted on July 8, 2021.