Unlike Aaronson, he actually is on the forefront of Busy Beaver research, and is one of the people behind the https://bbchallenge.org website
Extremely bad ad hominem, I enjoyed Aaronson's read, nothing wrong with it.
Colloquially, I understand it's easy to think it means "saying something about someone that could be interpreted negatively" because that's the context it is read in it when it is used.
The meaning is saying a logical argument is incorrect because of who wrote the argument.
>If you want to learn about actual Busy Beaver results [...]
This is saying there is no discussion of the results in the article, which is not true.
>Unlike Aaronson, he actually is on the forefront of Busy Beaver research [...]
This implies Aaronson has no (or lesser) authority on the subject and suggests we should listen to somebody else who purportedly has more.
Nowhere in @NooneAtAll3's comment is there an argument made against/for the contents of the article, an example of that would be:
"Aaronson mentions X but this is not correct because Y" or something along those lines.
Instead, the comment, in it's full extent, is either discrediting (perhaps unintentionally) and/or appealing to the authority of people involved. That's ad hominem.