The soft-bricks are not due to the kernel, I'm a beta tester for the S2 on the MIUI English forums. My phone has been soft-bricked about 5-7 now, 3 of those times using different kernels. MIUI confirmed it was a ROM issue about 2-3 weeks ago and they still haven't resolved the issue.
- If you are having issues with LBE, try downloading BusyBox from the android market and install the latest version (worked for my root issues).
- They mean delete LBE from the /system/app/ directory and install SuperSU from the market.