Dang-Khoa Do, Spigot algorithm and reliable computation of natural logarithm, Reliable Computing 10 (2004) 489-500, gives spigot algorithms for computing various logarithms. I didn't look at it closely enough to tell whether $\log23$ is amenable to Do's methods.
EDIT: Incidentally, OP is quite correct to relate the difficulty to the Mersenne connection. See the top of page 11 of < Bailey, Borwein, and Plouffe, On the rapid computation of various polylogarithmic constants.