According to Answer appears automatically converted as a comment on meta.se:
Trivial answers containing a link to another question in the network are automatically converted to comments on the question
I came across this answer on dba.se:
I solved that issue by referring below link. stackoverflow.com/a/57307231/11701617
...together with an apparently duplicate comment:
The user has 1 rep (so can 't comment directly) and there have been no moderation actions on this Q & A, so I can only assume the automatic conversion process was responsible.
Why wasn't the answer deleted when the comment was created?
- The comment has a timestamp of 2019-08-01 10:50:15Z
- The answer has a timestamp of 2019-08-01 10:51:44Z (later)
There are no deleted answers at the time of writing, and that user has taken to actions beyond that one answer and comment.