To quote from the paper, “central banks would find it difficult, (even ex post) to defend potentially unpopular measures, precisely because they succeeded in maintaining financial stability.” And any perceived failures on the financial stability front have the potential to undermine monetary policy independence through a general loss of credibility of the central bank.
BIS central bankers’ speeches  5  A final issue is the debate around the optimal level of inflation. In particular, is the 2 per cent inflation target norm in advanced economies too low? Olivier Blanchard at the IMF mooted this in 2010, but the idea persists, and was recently raised again by Paul Krugman.