I’m not sure why I had never manually done the fix before, but I’ve had issues1 2 with the Syndication Links plugin showing icons for the reading.am service and my old chrisaldrich.wordpress.com site, which I primarily use as a pseudo-mirror/backup to my primary site. I figured there had to be a way to force them in instead of relying on the set up to process the links and show something. Reading.am doesn’t work because there isn’t an svg available for it and though there’s a WordPress icon, the plugin’s parser doesn’t seem to be able to recognize the subdomain properly.
Within the code at class-syn-link-domain-icon-map.php, I added the following two lines to the obvious spot in the list within the code to fix the icon issues I was having:
'chrisaldrich.wordpress.com' => 'wordpress',
'reading.am' => 'book',

I then reuploaded the edited file to my server. Essentially I’m hard-coding the domain name and the default icon I’d like to have the plugin display.
If the plugin is updated, I’ll obviously have to manually add them again, but the disappearance of the icons again will be pretty obvious and this post will document the necessary changes.
Although upon tweaking this I’m noticing that the reading.am icon isn’t working (I also tried ‘website’ instead of ‘book’ but that didn’t work either). Perhaps the .am tld is causing an issue? Alas…
I suspect that there’s some other bug hiding in the works as one or both of the two types of links above should default to the generic ‘website’ icon when a syndication link exists, but the system isn’t able to specify a particular icon. There may be some small if/else bug hiding in the logic of the plugin.