???

I have reflashed the emmc at least 5 times since I got my n900. No problems.

No, you won't brick your phone. It's pretty much impossible to brick an n900.

1) download the latest global pr 1.2, and the latest vaniilla emmc

2) flash pr 1.2 (don't use the -R flag)

3) immediately after flash the latest emmc (this time use the -R)

4) done