I'd consider the question you linked to be a duplicate of this:
Is it appropriate to comment on people's accept rate?
While speaking specifically about accept rate, I consider it to be the canonical reference about commenting to users about how the site works, instead of focusing on the question.
The fact of the matter is that a user doesn't want to accept an answer or upvote, they are still completely welcome on Stack Overflow. There is nothing that states that they have to participate in the gamification elements of the site.
That said, taking your statement (emphasis mine):
with the moderator casperOne about a comment to one of my own answers asking the user to accept my answer
That's the problem with your comment as your campaigning for the acceptance of your answer.
Also note these other comments from you:
@JohnB: Great! What was the final solution? Oh and please don't forget to accept my answer by clicking the check mark to the left of it.
@tesicg: You are welcome :-) Please don't forget to accept my answer by clicking the checkmark to the left of it.
All of these are urging the person to use the site, yes, but you're also doing it to your benefit. It's one thing to ask "how can I educate a user on how the site works", it's another to do it to inflate your rep.
This one in particular is my favorite:
@user1447851: No problem. I upvoted your question, so you got some reputation. :-) Accepting my answer using the checkmark to the left will give you another two rep.
Basically, you're trying to inflate your rep by making it seem like you're doing the user a favor in getting them two more rep. Nice work.
That said, comments are not the place to inform users how to use the site. They are certainly not the place to encourage users to perform actions to inflate your reputation.
If you truly want to encourage users how to use the site, do so in a neutral way, and don't do it in the comments.
If they have contact information in their profile, feel free to contact them through there. However, I wouldn't take that as an invitation to spam them about it.