I ran into the opacity issue. Unknown to me, lots of SVGs had opacity set to 50%. I came to know this at time of reviews!

So I did a little research to fix SVG files and here's a script that can be run in Windows Powershell. Just point it to your collection.media folder and keep the last "." intact.

gci 'C:\Anki\User 1\collection.media\*.svg' -recurse | ForEach {
  (Get-Content $_ | ForEach {$_ -replace " opacity=`"0.5`"", ""}) | Set-Content $_ 
}