Paper accepted with no report? I submitted a 60-page paper to a reasonable math journal (Journal of Algebra) about 6 months ago. A few days ago I received an email stating that my paper was accepted. I did not get a referee report. I did not get any comments on my paper.
 Just an acceptance notice.

Is this usual? it seems very strange to me that the referee has absolutely no comment on a 60-page paper!

Should I ask the editor what happened?
Yes, asking the editor about this seems very reasonable, as not getting any sort of report from the reviewers sounds like an error.
(I have published one paper in J. Algebra, and we did get a reviewer report, just as one would expect).