> However, the "Show HN" phrase is only used for self promotion I think, so even without the "I", anyone familiar with the convention will know it's self promotion.

I think that's an extremely cynical view though a common one. I've never thought of "Show HN" as self promotion if it doesn't include "I" unless I go through to the actual product/library/post and find it full of self promotion. I agree with you that a post that doesn't include "I" can be self promotion but I don't think it always is even if the person made/worked on it.

"Show HN: XYZ and LLM library in rust" to me is informational. It's point is, more often than not, to inform people of something they might get use out of. I know that's true when I've posted something like that. It's meaning is "here's a useful resource that was just created". Sure I get pleasure from knowing I helped people with something but I'm not trying to promote myself, I'm trying to promote the library/post/info.

"Show HN: I made an LLM Library in rust" to me is self promotional. It might be useful to others but it's intent was clearly self promotion given the subject is "I", not the library/post/product.