with the default launcher it doesn't log the error anywhere, although the problem still seems to happen. i noticed it with multimc5's error logger. not sure how helpful will those logs be.
if you change any value (for example, set textscrollingspeed to 3), then exit minecraft and return, the value resets back to original 2.
a few times i saw options i don't normally see, there was an item section with configurable mobtalker item, and general's had MislDebugOutput and version. not anymore. is that how it should be now?
if under multimc, no other mod's config can also change. in regular loader it seems only mobtalker's affected, forge's config changes.