Yes.

A named or pseudonymous source necessarily has an associated reputation, but an anonymous source has no reputation at all.

A reputation for lying is stronger evidence that the information might be false than is no reputation at all.

I disagree. We must treat every anonymous source as if it has that reputation for lying, as otherwise a source can simply become anonymous to improve the credibility of their lies.

Until, of course, a source presents evidence, at which point we evaluate the credibility of the evidence instead of the source.

Not really...

Even taking all emotion out of it, a story from a source that is probably a lie convey s more emotion than a story from a completely unknown source.

Maybe not by definition, but it's almost irrelevant because a not anonymous source is so much easier to verify / disprove. Sure, in theory an anonymous source could be 100% accurate, but since they are very tricky to back up, they almost always have the effect of stirring the pot without resolving anything, and thus quite often appear as nothing more than attempts to do just that. And after a while, people unsurprisingly start to treat them as such.

Well, certainly it's significantly more credible if it's an actual Github employee putting their name on it and standing behind that sort of statement. At least in that case you would hope that the possible repercussions of making such a bold lie would prevent most people from lying about something like that.