Comments are often full of obsolete information, like someone's display name. If @user-1248177 changes their display name to Steve your comment won't be updated. We are all generally fine with that. There has been no suggestion anywhere that you are obliged to monitor every comment you have ever written to see if it has become obsolete.
That said, if @user-1248177 were to ping you and say that "she" is how to refer to her, (there's no need for a gender change or a choice, you wrote yourself that you had just assumed @user-1248177 was "he"), it would be nice if you would change your comment in accordance with the information you had just gained. Since comments can't be edited (except within 5 minutes), you would have to delete it and repost it with the correct pronoun. (If there's a reason you can't do that, you could flag and ask a mod to edit it, but that might not succeed.)
If that level of future work worries you, write your comments neutrally to begin with. For example:
You should read the answer provided by @user-1248177; it has more information than I provide on this specific point.
The only mention in the CoC of avoiding pronouns is if you know a person's pronouns and write unnaturally to avoid using them for some people, while cheerfully using them for everyone else. Always avoiding them prevents this sort of problem. And as an extra bonus, it prevents the minor sting of invisibility many women on these sites feel when people praise them while assuming they are men. Win-win.