There's no comprehensive list of guidelines; if there were, people would start doing all the things not listed. But if you just stick to straightforward description you should be fine. As a bonus, that's what HN readers tend greatly to prefer, and it leaves plenty of room for creativity.

The visual gimmick thing comes up every month but really isn't fair to the other users posting here.

By gunk I meant fluffy comments like https://news.ycombinator.com/item?id=16285856, which don't really belong on HN. They wouldn't be harmful if there were just one or two, but they tend to proliferate to the point where the site would be smothered by fluff if we let it. And the Who Is Hiring thread is a particularly bad place for them.