Self-promotion is seen on the internet as underhanded and suspicious but I really don't mind it when it comes to creating links between communists. What's the difference between self-promotion and other promotion? Submitting a link to your own work is bad, but asking your friend to do it is good? That doesn't make any sense.
This is why I've been pro-self-promotion for years, and allow it in every community I've moderated as far back as antifastonetoss on Reddit. There we even worked with antifascist artists to promote their work on the subreddit.
The only limitation I would put on it is that you have to interact with the questions and comments to some extent. But that's about it. This creates trust and is the basis of social media: interaction (it it only went one way then you'd act more like a TV or radio channel).
Stamping down on self-promotion only shows that you're scared of being one-upped or eclipsed as a mod. We rarely have had issues with self-promotion, and if it helps other comrades boost their work, then that's great.
Reddit is terrible for this. Most subreddits hate self-promotion of any kind and will remove your posts over it, or even ban you from the start. Why? Your community doesn't care that someone posted their own work. They will open the post, comment and vote on it by themselves. Why do you need to be so controlling? It's ludicrous to remove a post that has say 15 upvotes, signalling people like it, just because you want to control the flow of information in your subreddit.
I've honestly rarely had excesses. Excesses are hard to define but like I said, I do expect you interact at least a little bit with the community. This lets us know a little bit more about you and vet you organically. I've had on Discord a person who only wanted to recruit for their party and never interacted with anything outside of that. They would only talk about their party and post links to their newspaper, ignoring any question pinged to them that wasn't about their party. That was fine for a long time and we didn't really moderate on it either, but eventually other members started feeling like they were just using us and weren't interested in the work we were doing. When we brought this up to them they simply stopped using the server but remained in it.
In this case yes it can feel suspicious, like you're just using an existing community. But it also allowed us to learn more about their party and their work.
And we've had self-promoters who didn't really interact on Lemmygrad too, but eventually the community organized to discuss what to do with them, forcing them to reply. Like I said the only limitation I would put on self-promotion is that you at least show you're not just spamming everywhere.
But even then people will end up discussing your posts regardless of mod involvement. They will ask questions under the post and others will reply. So what's the actual problem? That the OP is posting and not interacting? Why does that matter?
Really the only thing that should matter is why they are posting and where to. We had someone here who posted to a sort of incel blog if you remember and eventually took action against that. If it's a website I don't know then I might ask questions and need an answer from OP, but if it's a source I know then what's the harm?
Basically think of it this way. In lib spaces people willfully and readily post to the New York Times, Wikipedia, CNN, etc. We don't ask them if they're self-promoting. These organizations have a huge contingent of fans ready to post their links everywhere at a moment's notice. When you don't have that, you have to do it yourself. The first one is apparently not a problem, the second is almost always seen as one.
This is the contradiction most places, especially Reddit, find themselves in. They create large communities and it's super easy to get noticed on Reddit because the work of creating a following has already been done. But they are able to create this community because people post in it and interact with it, leading to more people joining it. Without these members posting, they would have nothing to moderate. It then leads to another contradiction between moderatorship and community as they have opposite interests.
This is also why we rely on community self-management on Lemmygrad and often take time to respond to controversies on the platform, to soften that contradiction. We can't make it disappear, but we can soften its effects.