I believed, and believe, the question should be closed
Consistency is very difficult in the real world. It's no surprise that it's just as difficult (if not more so) in a virtual world. That assumes this is a problem with consistency. Perhaps it isn't. Rules change over time. I'll mention one momentarily. But as a consequence, a question that was on-topic a year ago might no longer be on-topic. I'll let others decide if my 1-year-old question might now deserve to be closed, but if it is as vaguely about world building as I believe the linked question to be, then it should be closed.
While questions about transportation are common on this site and have been accepted as a legitimate world building context probably from the site's beginnings, a giant cutting disk isn't so obvious. There are a lot of problems to be solved long before the speed of the outer edge of the wheel can be considered.
Cutting disks work because the force holding them in place is greater than the resistance met during the cutting process and the torque caused by the motor spinning the wheel. Cutting a planet means using something akin to a moon (or an unbelievable set of rocket engines) to hold the disk while still using some engines to hold the moonish object in place and above the planet you're trying to cut. Without the blessing of gravity holding the cutter-user's feet to the ground, the moon, no matter how massive, will begin to shift due to the forces of use — and that doesn't even account for the problem of overcoming gravitic attraction.
Therefore, considering how many other problems involving physics the idea has, asking about the disk edge hitting the speed of light was, IMO, superfluous, and therefore seemed to me more an exercise in physics ("if you hold a ladder against a wall and pull the bottom rung at a consistent velocity will the top of the ladder exceed the speed of light before hitting the floor?") than an actual world building effort ("I'm designing a world with strong, highly-focused winds that has the capacity to push the ladder's bottom rung as described.") Like I said, I couldn't see the world building application.
While physics questions are common and popular on this site, this site is not dedicated to answering physics questions. That's the job of Physics.SE. Based on our real-world question debate so-called "pure physics questions" are permissible if and only if they have a world building context. This is important. One of the primary concerns in that debate was that WorldBuilding.SE would become the dumping ground for everyone who couldn't get their question answered elsewhere or was simply too lazy to go elsewhere. The requirement for a world building context was the solution to that particular issue.
Can I be convinced to reopen the question? Sure I can! In fact, I'm delighted to invite the OP to rewrite the question to make it better conform to the site's expectations. At this point, I'd recommend posting the question in our Sandbox and asking for input from the community about how to recraft it to avoid closure. Once the issues are addressed, edit the original question or ask a new one as needed/recommended by the community.
But is there a bias against newer users?
Not that I've seen. I've had my own questions closed at far higher levels of reputation than those of the linked Q's OP. Higher rep users are, not surprisingly, the one most active on the site and therefore the ones most likely to be involved in closing any question. It's a bit like asking a policeman if he/she's biased against new city residents simply because he's lived there a long time. No, he's just doing his job (most likely to vote) and the new resident hasn't yet figured out all the rules (most likely to not understand the rules).
Finally, I want to second Elemtilas' statement about popularity
We've had to make this point a number of times. Popularity != suitability. When most people cast a vote, it's on the emotional basis of "I like this question!" not the unemotional basis of "this question meets all our rules and forwards everyone's understanding of world building." When it comes to discussions about why any particular question is closed, its popularity is irrelevant.
In fact, considering your concerns about consistency, the popularity serves only to underscore with three or more lines the simple fact that consistency is difficult to achieve.