Could Citi be buying back shares quitely right now?
I don't think it's anything like that. Simple supply and demand. With a ton of volume the curve is a lot smoother than stocks with less outstanding shares (and hence less daily trading volume). Look at a chart with less shares outstanding (GS for example) and their chart will be a lot bumpier, with wild swings, than a comparable daily chart for Citi.
People love to theorize that Citi is secretly buying back shares, but if they were, SEC & FASB requires they disclose this in their financials. Evidence of a secret share buyback just does not show up.
Yes, this is a basic tenet of GAAP. Any use of cash must be accounted for. The balance sheet equation of A = L + E must balance. If assets go down (cash used for share buyback), then equity must go down (to reflect fewer number of common shares outstanding). This has not been happening according to Citi's balance sheet.
And yes, Citi must disclose information like this. FASB rules are very strict.
This just means you like speculative positions. Citi has it's days. Some good some bad. Look for big swings on Friday. In the end, the Citi investment thesis is a play on the value of the dollar and the economic recovery. Everything else is just noise.