I've done a custom.css modification as follows.....
.ipsComment_content .ipsType_richText, .ipsApp .cke_contents,
[data-pageapp="blog"][data-pagecontroller="entry"] .ipsType_richText{
color: #111;
font-size: 16px;
font-weight: 500;
}
.....which relates to the individual post views.
If you empty your browser cache you'll see that the text is now bigger, darker, and the font weight has increased.
Those of you using the Customiser can test by turning it off and checking if the default view has improved enough for you.
If it hasn't then turn it back on again.