Are they not receiving it at all? Because there is a small bug, which doesn’t let you know that you have received the badge, but you can see it if you go to Profile > Badges
I have had this, the date of April 2017 is given because that is when the post that received its 10th like or in your case 25 for a good reply (albeit only given yesterday or today) was originally posted.
They are not receiving it at all, as far as I can tell. I’m looking at /u/username/badges. It’s not just a matter of an unexpected date. I think my methodology is correct because I see the badge for 1 out of 4 users.
Yes, it’s public. I don’t see a difference between the topic in which the one successful user posted, and the topics in which the unsuccessful three users posted.