I'm not a good marketer, so take what I say with a grain of salt, but the only thing I've found that works is replying to relevant comments in popular threads with neutral looking promotional material (e.g. github links). A well placed reply in a hot thread will easily drive 10x the value of a blog post.
I think it's possible to do it ethically, but anything that works is going to get gamed.
It's a pretty dark dystopian future where the only way for anyone to hear about anything is advertising or paid promotion by influencers because we're so aggressive about policing individuals marketing themselves.
