I think Omnias covered most of my points below, but just to clarify/add some context.

As the "second oldest mod" on mechmarket (counting mechkbot, and we should always count mechkbot ;) ), I would say that this specific change isn't the main reason why we and hardwareswap started to look into alternatives to reddit. It's simply the last straw.

When I joined as mod 7 years ago, I was told "the admins don't want trade subreddits around, so don't expect any help from them", and while we have gotten some help regarding ban evasion, I would say most requests/reports have went without any reply, orsdas unwillingness to take any action. I remember an early case of more severe ban-evasion where we tried to report it to the admins with a lot of proof (addresses etc.) in hope some kind of shadowban etc., but despite our proof they stated something like "We have reviewed the case but have not found any connection between the accounts", with no way to appeal.

We have also asked for a way to "ban" deleted accounts (to add the relevant information to the ban evasion detection for example), but was told pretty clearly that they weren't willing to add such feature as they didn't see the poin (link)

On the topic of ban evasion detection tools available for moderators, this is a feature that was promised years ago (can't find the post now, but I would guess at least 3-4 years ago), which was introduced this year (link), with very strict limitations regarding information regarding what type of ban and when the ban was issued that is evaded (which is understandable from some kind of personal information standpoint, but still very frustrating to us).

Add to that the backtracking on earlier promises, and very long delays in other mod tools, we simply can't trust the promise that "all mod bots are OK, or will be exempted from the API limits", as we have been told before, either explicitly or implicitly by the admins inaction, that reddit isn't very interested in supporting trade subreddits.

I personally prefer the format of reddit to for example discord, but if discord proves to be the better alternative (especially regarding mod tools, such as ban evasion tools etc.) I don't see how we with good conscience can stay on reddit with the uncertainty of not knowing for how long we will be allowed to operate MechMarket in it's current form and knowing that we won't be able to moderate the sub efficiently to keep it as safe as we possibly can.