How to reproduce?
Create a wiki-page with the following content:
You will see that the double-spaces in the block-code is properly displayed, but is not in the inline-code.
As this does really pose a problem with code that contains double-spaces, this should probably be fixed.
Tested with both Firefox and Chrome (both latest version)
This can be fixed either using <pre> or using the CSS white-space property: "white-space:pre;" for inline code.
You are aware that the 'inline' code is only a formatting style? With other words: wrapping with double single quotes, applies only a textstyle with monospace font, not more so far.
As Klap-in says, not a bug. double quotes applies monospace font. It does not, and is not intended to change, white space behaviour.
If this is something you would really like to have in your wiki, add
to your conf/userstyle.css