On this whole thing about whether or not people on Reddit like self promotion topic is a bit easy to figure out. Just look around in the sub reddit that is about the material your video covers. If you're a gaming channel, then looking at the rules of the sub reddit is important and then checking out the kind of content people are upvoting and what isn't getting upvotes.
Each sub reddit is a little different. Take any MOBA sub reddit for an example. If you post just regular posts in other people's threads you can get down voted for no reason. So when you post videos and self promote, it's possible that your content will get completely ignored or get a couple upvotes. Where as in other gaming sub reddits this wouldn't be the case. However, this will most likely be the case for any game that people consider competitive. Why? Because people will smell the BS in your post and call you out on it. Post content that shows off your experience, knowledge, skill, etc. and you'll be fine.
Of course all of this is different when it comes to other topical material on Reddit. When it comes to cooking or music, things are a bit different than it is with competitive video games. You'll probably receive a lot more warming welcome into the community's fold. But as already mentioned it's important to try and be a part of the community rather than just posting your content. It's spammy. People don't like spammy things.
Another thing to make sure that you could do is try and create content that is adding value or addressing a problem or issue your channel's target audience might have. That way when you share it on Reddit and other social media platforms, you'll get a much more positive reception towards your content.
You don't even need to figure all this out with your own content. You could test this out by using other people's content instead and trying it with a variety of different approaches to the content.
As for being shadow banned, could always make another account or message one of the sub reddit mods and find out. If you are, then ask why. They could very well unban you if you communicate with them. Just an idea if that's the case.