Instances where mod can lock comments?

Hi all.

I had taken a break from posting to my magazine due to the lacking in effective moderation tools, especially bans not federating, an issue I don't see a solution for happening any time soon, but I'd quite like too post again. So my question:

I have seen mention in passing of mods saying they have locked a post to comments, and specifically yesterday a mod from slrpnk.net said they were going "to disable public posting and lock all threads". Which made me think that that might work for me.

However, from kbin it looks like I can still comment on posts in the community they said they were locking, so is this an instance-only solution, in a similar way to what banning users seems to be, where it only works locally, but people on other instances can go on interacting externally without issue (and without the mods being able to do anything about those external interactions)?

Is there an existing* way to just post image links to the fediverse without having to worry about moderating the comments because they're disabled across all instances? I'm not in it for the internet points and am more than happy for people to repost the content I share if they want to have their own conversations, I just can't take it on myself to keep the trash out if I can't actually keep it out.

Thanks!

*I don't have the knowledge or spare time and energy to invest in learning and then maintaining a self-hosting situation, so that won't work for me