Add default class to anchor link

Yeah I also need this feature

If I remember correctly, the CKEditor 4 version of anchor link adds both an id and name attribute to all anchors. Maybe you could select <a> elements that have both attributes? For example:

a[id][name] {
  /* your styles here */
}

Depending on other styles in play, you might have to use !important to get them to work.

This assumes your text format/filter is allowing both attributes through to the rendered content