Probably? I couldn't tell you where to find it though. I've been reading Highlander fic for almost eleven years and I just know that I've seen numerous fics mention SCA memberships.

Is there a Highlander fic finding comm? If there isn't, why not?

You could try searching around on AO3 or HLfiction? Seventh Dimension is still up (and has way more fic than HLfiction even if it hasn't been updated in half a decade), but I wouldn't envy your searching there.

Does hl_flash allow fic finding questions?

Last edit, promise. What about asking at highlander? It could use some more activity.