Using typecasting to remove gcc compiler warnings

I am doing embedded ARM programming with gcc 4.9. I've been using the -Wconversion switch because it's in my company's default dev tool configuration. I'm using the stdint.h types (uint8_t, uint32_t, etc).

The compiler creates warnings every time I perform a compound assignment or even simple addition. For example:

uint8_t u8 = 0;
uint16_t u16;

// These cause warnings:
u8 += 2;
u8 = u16 >> 8;

The "common method" to fix this is to use casts, as discussed here and here:

u8 = (uint8_t)(u8 + 2);
u8 = (uint8_t)(u16 >> 8);

In addition to this being ugly, I keep running into convincing evidence that casting is generally bad practice.

My questions:

1. Why is it bad to use typecasts in this way?
2. Do I lose anything by simply omitting -Wconversion and letting the compiler do implicit conversions for me?

via Chebli Mohamed