CSS that works on #collection fails on #post

Any idea why

#collection h5, #subpage h5, #post h5 {
text-align: center;
}

works on collection pages and subpages but not on post pages? There doesn’t appear to be anything in write.css that would override this custom CSS on posts but not on the main page.

I am at a loss.

I don’t even remember what the above was about or if I needed it or if I solved it but here’s a new one in a similar vein:

I am toying with normalizing posts to look like the collection/index page and while everything is coming along swimmingly on font-size and line-height and such, the spacing between paragraphs is different and for the life of me I cannot find anything in the css file to explain this.

What am I missing?