Two ways:

1. Look at the domain. If it says "WSJ", don't click.

2. Accept the fact that there are people on HN who pay for WSJ, BusinessWeek, NY Times, etc. (as I do). These people like to read and comment on articles that are professionally written, edited, and fact-checked, despite having to pay for them. If this isn't what you want, that's OK. Let those who do prefer this sort of journalism read and comment on it without chiming in about the fact that it's not "free."