All paragraphs had a blank line between them, both with and without the p end tag. The p opening tag was always at the top-left, with no gap between it and the content.
So, for example:
<p>Cheats open the doorway for casual play. They make it easier for disabled players to enjoy the same things as their peers, and allow people to skip parts of a game that <em>they bought</em> that they find too difficult.</p>
<p>Unfortunately, cheats are going away, because of extensive online play, and a more corporate approach to developing games that despises anything hidden.</p>
Versus: <p>Cheats open the doorway for casual play. They make it easier for disabled players to enjoy the same things as their peers, and allow people to skip parts of a game that <em>they bought</em> that they find too difficult.
<p>Unfortunately, cheats are going away, because of extensive online play, and a more corporate approach to developing games that despises anything hidden.
(You can also discount CSS from having a major effect. Less than a hundred lines of styles, where most rules are no more complicated than: `p { font-family: sans-serif; }`. No whitespace rules.)However, if you wanted to look at this in a more scientific way - it should be entirely possible to generate test cases fairly easily, given the simplicity of the text data I saw my results with.