This has been fixed in the latest update B1587
It is possible to fix it without updating the installation, by updating the .css files directly:
Replace this file:
/WAF/Skins/Global/General.css
with the enclosed version.
Once the file is uploaded, delete all occurences of files with this name pattern:
/WAF/Skins/Global/waf.all.min.****.css
Reload the UI in the browser and it should regenerate the new css file and selected text should be highlighted with blue.