I always use
As someone said, ...in the comment or answers to respond peoples..
But I happen to see someone’s comments are
As you say,
As someone say
I cannot determine whether there are problems in the tense?
While it is true that references of this sort are to things said in the past, it is conventional and indeed reasonable to treat them as present.
What underlies this is the notion that any idea you have advanced in the course of the current conversation is still “present”, still under discussion.
Academic discourse in the humanities (but not, apparently, the social sciences) treats even very old articles in the same way: it is presumed that a disputant continues to hold a position taken up in the past, until it is explicitly withdrawn. And long-dead authors of literary or historical or philosophical works are held to be still “present” in their works as long as readers are still engaging with them: “As Aristotle says,”, “As Shakespeare says”, “As Gibbon says”.