I gave about an hour ago a one-line answer to this question, stating that a finitely generated algebra over a field is noetherian, and that a previous answer (by me, among others) had shown that the algebra was not noetherian.
My answer was removed and replaced by a comment, under which stood the (unsigned) explanation that the answer was trivial and hence converted to a comment.
That the answer was trivial is relative: it tautologically wasn't for the OP but it is certainly also true that anyone with a moderate command of commutative algebra will find it obvious.
Anyway, my rationale is to keep answers and comments disjoint: if someone asked how much is $2+2$, I would answer $4$ in an answer box and not in a comment. Call me literal-minded if you wish...

Edit
I thought the conversion to a comment had been done by a moderator, but Martin's comment below and Mad Scientist's answer explain that it is actually an automated process.
I apologize to all, but especially to the moderators, for this misunderstanding on my part.

• This is an automated process, executed if the software decides that the answer contains too little information besides a link to another answer. See: What constitutes a trivial answer? and Answer appeared automatically converted to a comment. – Martin Jan 10 '13 at 9:33
• Ah, I see, thanks a lot for your answer Martin: +1. The software "decision" was wrong: my answer did not consist of a link: the link was there to explain why my answer applied! Anyway, I will delete my question. – Georges Elencwajg Jan 10 '13 at 9:39
• Oops, now the software doesn't allow me to delete my question, because there is an answer to it! I have some strong opinions about this software but I won't be able to formulate them in decent language... – Georges Elencwajg Jan 10 '13 at 9:45
• Automated "low quality" check, "short answer" redirection, automated reviewer audits... StackExchange is becoming a virtual city patrolled by an army of RoboCops with limited artificial vision and a handful of bugs in their software. – user53153 Jan 10 '13 at 21:46