Some spam gets onto the site most days. Usually we spot it quite quickly, and it gets deleted before most of you will even be aware. For example, the comment that you refer to was deleted within 10 minutes of it being posted, and was gone long before your forum post.
What we can't do is recall the notification messages that are automatically mailed to anybody who has subscribed to get alerts to new content or updates.
We've got various measures in place to keep the spam bots out, but the only way to make this totally effective is to require every post or comment to be moderated before it goes live on the site. You simply can't do that on a community-based website.
To give you an indication of the scale of the problem, just one of the tools that we use has scanned 22635 attempted actions on this site (that's registrations and the posting of content). Of those, it has blocked 16543 for being a suspected spam source.
It's still incredibly frustrating when a spam post does get onto the site, but the problem is as under control as it possibly could be.