Although the currency didn't leave its range, that spike spurred renewed speculation that the peg could snap. To be sure, bets the peg isn't long for this world have cropped up perennially throughout its 32-year history without any sign the peg is anything but firm.
"Hong Kong -- the HKMA, and the Hong Kong government -- have a track record of defending the peg and maintaining the financial integrity of Hong Kong and I don't see that that's going to change anytime soon," Richard Titherington, chief investment officer and head of Asia-Pacific equities at JPMorgan Asset Management, told CNBC's Squawk Box Thursday. "There's no reason to think the peg is going to break."
That hasn't stopped the speculators from laying chips on it, said Angus Nicholson, a market analyst at spreadbettor IG, in a note Thursday.
"While the HKD has withstood rampant speculation before during the Asian Financial Crisis and the SARS crisis, short bets face at worst a move to HK$7.75 (the band being HK$7.75-HK$7.85) against them and anywhere from a 20-50 percent upside if the peg were broken," Nicholson said. "The risk-reward balance of the trade makes it compelling even if it has a low likelihood of eventuating."
The protectorate also faces pressure from outflows, particularly from its stock market. The drop in the HSCEI -- Hong Kong-listed shares of large China companies -- is pressuring derivatives tied to the index, particularly from South Korean investors, the Financial Times reported Wednesday.
Around $40 billion worth of HSCEI-tied "autocallables" -- a type of structured derivative product that pays investors capital and interest if the index stays within a stated band, but creates losses below that level -- were outstanding at the end of 2015, Korea Securities Depository data show, the FT reported. The index level at which most investors will feel the pain is around 7,800, the FT reported -- that's within spitting distance of Thursday's close at 7,835.64.
For foreign investors in Hong Kong, the Hong Kong dollar peg may also boost the attractiveness of selling the protectorate's assets. While the peg kept the local currency steady against the greenback, competing currencies around the region have dropped.
Against South Korea's won, for example, the greenback is more than 3 percent stronger just since the start of the year. That means a South Korean investor would see foreign-exchange gains when selling Hong Kong dollar assets and converting back into won.