What exactly is Twitter sample size? If it means "the number of records processed", why does it vary over time?

One way to approach the "significance" problem for smaller communities like HN is to create larger bins of misspellings/correct spellings. However, I don't think you're going to see many "anyways" or "yea" on HN at all, much less significant fluctuations over time.

Finally, an interesting question might be to what extent individuals fluctuate in their ARI/FK levels in different contexts. What if a poster in /r/lolcats writes a very asinine comment but then goes five minutes later to /r/programming to speak intelligently. Or is it the case that an idiot is an idiot, regardless of context?