but when you have very large paragraphs. this is very difficult to read.

The same whitespace that's also after each word. That doesn't make it easier to find at all.

The typographer Jan Tschichold experimented with this in the thirties, though I think he recommended space-period-space to separate sentences rather than period-space-capital, and not bothering with a period at the end of a paragraph.

The writer double spaces too in his post, which does make it more readable. Ironically, he mainly argues against hitting the shift key too many times.

I don't really see how double-spacing's any different from capitalizing + single-spacing, except the second is much more readable to me.

Double spacing in HTML doesn't sound a whole lot easier either. You'd either have to write something that changes one of the spaces to   or do it by hand...