If I am the copyright holder of a project licensed under the MIT license, can I change the name in the copyright notice? For example after a name change or changing to/from a pseudonym. Note that (unlike the other questions that have been posted about this) this is not about someone else's project, but one that is owned exclusively by myself.
If you are the sole copyright holder, then the answer is very simple: You are not bound by any license, so you are allowed to do anything you want including those things that most licenses forbid.
If you are not the sole copyright holder (e.g. you accepted contributions from others), then things become more complicated but not all is lost.
If there are only a few copyright holders, you can just formally ask for their approval to make those changes to the copyright notices. And some jurisdictions also allow in their copyright laws that factual errors in copyright notices are corrected.
And lastly, copyright notices don't carry that much legal weight nowadays. At best, they are an aid in establishing who owns the copyrights and if you can make a plausible case that you used that name/pseudonym around the time mentioned in the copyright notice, then that should be sufficient to establish you as a copyright holder.