According to what standard is it not rational behavior? New information emerged regarding the current perception of XIN (in the form of the price drop) and regarding its short-term future performance. JB changed his strategy accordingly. This is what rational investors do; they adapt to new information. In JB's case, it has paid off; he's up big with STV and still has the option of buying back into XIN at a lower price than the one at which he got out.