MG,
All I did was add !important at the end of the CSS for the margin. Whether they have a css directory or not is irrelevant, the Links Shortcode plugin is sending css to the browser and is doing so after the MimeTypes Link Icons plugin. The result was that the latter overrode the previously send css. The !important directive I now added basically tells the browser to ignore the override and respect the original css from MimeTypes Link Icons.
Another way to do this would be to change the loading priority of the plugins - which would then load the MTLI css after the LS css -, though that might in rare events cause conflicts with other plugins.
So yes, you could ask the LS plugin authors to lower the priority for their plugin.
You could also try the 'Asynchronous Replacement' option (last one on the MTLI options page), I haven't tested it, but that might just solve the issue without any code changes.
Would you let me know whether the Asynchronous Replacement option worked for you ? If so, no change will be made to the code in general.
If it doesn't, I'll post a link to this thread in the bug report thread I opened yesterday which hopefully will get picked up before a new release is send out.
Smile,
Juliette