We have been using salient in production for a number of client sites. While there have been some improvements to accessibility like Column Link Titles etc there are still some failures when running accessibility checkers on some core Salient options.  

One big issue that comes up is empty <a> anchor tags.  2 Big offenders are the Back to Top button and the Gallery slide links (vc_templates/vc_gallery.php) where the links with the class of "entire_slide_link" are concerned.  I've overridden the templates to include some spans with a class of "sr-only" with text in the link that says like "Back to Top" so that accessibility checkers and screen readers will not complain.  I would highly encourage your devs to take accessibility into account as this theme is already amazing and making it even easier for users with accessibility issues to navigate would help greatly.  We love the theme and growth so far and would like to see you take the next steps in making it usable for everyone!

Secondly, while it is technically standard practice to use the <i> element for icons now, accessibility checkers and screen readers have a hard time with that and would recommend changing any <i> elements for icons to use <span> instead.

Third, Video Player widgets should have a "title" attribute and an input in the widget where you can specify the title of that video for screenreaders.

Thanks and keep up the amazing work!