1.4.1 specifies a minimum luminosity contrast between text or diagrams and their backgrounds. Often diagrams include portions that convey information and other portions that are purely decorative; in such cases, shouldn't this criterion apply only to portions of the text or diagram that are functional or convey information? Large text used as a decorative element behind the text of a Web page is an example of purely decorative text, and in such cases you really need to retain low contrast with the background.
Change to read "Portions of text or diagrams that are not purely decorative have a luminosity contrast ratio of at least 5:1 when compared with their backgrounds."
The topic of contrast in diagrams became so complicated and uncertain that diagrams were removed from the provision. It now only applies to text and images of text.
RE: Decorative text, we do not require that decorative text need be high or low contrast. Just that there be sufficient contrast between non-decorative text and what is immediately around it. If the background of non-decorative text contains decorative text the contrast provision would apply. If not, we have no restrictions on it.