I argue that "fun" and "authenticity" are not two poles of one axis, but rather independent, perpendicular axes. So there can exist performances which are fun and authentic, fun and inauthentic, unfun and authentic, and unfun and inauthentic.
The "sweet spot" for SCA performance seems to be well up the "fun" axis and about centered on it. That's "SCA appropriate" - maybe inauthentic, but too much; maybe authentic, but not too much. It's close enough to modern to be accessible but also not "glaringly" modern. Ideally, it is somehow evocative of the Middle Ages "as they should have been" as well.
For examples, consider the collected works of (say) Mistress Rosalind Jehanne. "The Song of Roland" falls on the "authenic" side of the fun axis (but not too far - it is not, after all, a reconstruction of the chanson). "At the Battle of Maldon" ambitiously captures the alliteration of the original, but also imposes meter and rhyme on it. This fits it much more firmly into our modern performance idiom. It makes it more accessible - that's the second time I've used that word, and I think it's important. It's hard for something to be fun if you don't "get it." Mistress Rosalind's work is marvelously accessible and brings some actual medieval stories and themes to people who might otherwise assume it would be boring.
As I'm brainstorming ideas for a performance project, I find myself torn on this idea of accessibility. Part of me wants to lump it and strictly pursue Art (and you should probably imagine that word all in pretentious fancy Gothic letters). That's the part of me that's fascinated by the Anglo-Saxons and wants to try and bring their words and performance to life in the most accurate way I know how.
Then there's the bard part of me who wants a happy audience. While I do believe there would be people who would appreciate a very authentic re-creation, it is not going to hit that "fun" spot for most folks, because it won't be accessible. It'll be weird. Good-weird, hopefully, but weird all the same.
So I found myself pondering parallel performances: the "real" one and the "modernized" one. Say, the onion riddle in direct poetic translation vs. the onion riddle rewritten in three rhyming quatrains of iambic tetrameter and set to repeating music.
I don't think I really want to do that. I think I feel like I need to, to satisfy this imaginary audience. Maybe the brave thing is to try the weird performance and see how it flies.