The community is originally from lemmy.world, I subscribed on my own instance. In my example it was just “lemmyworldtest”, but a proper use-case would be to subscribe to lemmy.world/c/techsupport on my own instance and post an article to that community. Since the community has its home on lemmy.world, I would expect/need my post to be visible there in order to actually receive some support.
Also, at the time I’m writing this, your comment to my post is not yet visible on my own instance although I’m subscribed there as well.