I don't think it is a known thing why some articles come out with weird fonts/sizes. I looked in the editor, and there's a lot of HTML formatting tags before every individual paragraph in this post, but no obvious way to affect them one way or the other in the WYSIWYG. Manually deleting all the formatting tags would involve removing so much text that I'd be afraid to carve away actual content, so I'm leaving it for the original author, who will be more likely to notice something missing.