Imagine: You've worded a post so perfectly as to avoid orphaning the end of a sentence on a new line, its visual flow impeccable, only to discover a devastating inconsistency:
Posts on the Home feed are narrower than they appear on Profiles and the Post Editor Preview, by 25.833 pixels.
Also, the width of posts on Profiles and the Post Editor Preview are a weird fractional value? 649.833px wide, excluding padding. Posts on the Home feed are 624px wide, excluding padding.