It could be that google evaluates the keyword density and if it up to high they ding you but they also have said that they are not a fan of hidden elements. How would they know if they don’t read your CSS/JS? Is the algorithm smart enough to tell the difference between good hidden items and bad hidden items? Maybe. Should you err on the side of caution? Definitely.
Taking the chance on the -9999 indent is up to you and how good you think your chances are. You are hoping that they will see it as a design issue and not an SEO issue. I’ve used it and think it is worth the chance in some cases. Others might be more cautious. If you do use it, try and make it as unobtrusive as possible.
Blanketly saying to ignore the possibility of penalty seems dangerous to me and not a very good practice. Use caution and best practices. Write content for the user, not the search engines. Don’t try to trick google, it’ll bite you eventually. A lot of people thought they were smarter than the PHD’s google employs and have watched their business crumble with a small tweak to the algorithm.