XKCD

You can decide to pad "dog" with "qw34rty", like "dogqw34rtyqw34rtyqw34rtyqw34rtyqw34rtyqw34rtyqw34rtyqw34rtyqw34rtyqw34rtyqw34rtyqw34rtyqw34rty", and even if they are repetitions I doubt this will be on any rainbow table.

The magic is just to decide on a padding that in effect is random to the attacker, like "9fe8jn" repeated 20 times, added to simple dictionary words.

The point of the article is that, as long as one doesn't copy padding techniques from a friend, they are more secure passwords than a simple 10 characters random one.

The major problem with this is stupid sites that restrict password length, which by itself shows that the site security is not trustworthy, whatever secure password you choose.