How do you define "regular" and "sometimes"? At what point do you decide someone is "participating"?
If someone submits, say, 10 links to other (presumably interesting) sites for every 1 link to his own site, is that kosher? What if it's 4:1? 1:1?
How interesting do the other sites need to be? At one extreme is neat stuff that everyone likes and makes it to the home page (which benefits the "my own stuff" not at all, but certainly helps with karma). At the other is junk thrown in as filler to make that 10:1 ratio.
These are not idle questions. Especially when I think everyone in the HN community is aware of journalists' and bloggers' need to attract attention to their articles (which they, at least, believe are relevant). The question is how one can be an accepted member of the community _and_ also let people know what he created.