Why is enabling 8 bit control sequences not recommended?

./configure --help: **--enable-8bitctrls** enable 8 bit control sequences (not recommended) As far as I can tell, the only affected code is this part of src/command.C:

c
/*{{{ process non-printing single characters */
void ecb_hot
rxvt_term::process_nonprinting (unicode_t ch)
{
  switch (ch)
    {
//
// skipping non-relevant lines
//
#ifdef EIGHT_BIT_CONTROLS
      // 8-bit controls
      case 0x90:        /* DCS */
        process_dcs_seq ();
        break;
      case 0x9b:        /* CSI */
        process_csi_seq ();
        break;
      case 0x9d:        /* OSC */
        process_osc_seq ();
        break;
#endif
    }
}
/*}}} */

So, I suppose the problem is not with rvxt-unicode code itself. What bad things could happen if 8-bit control sequences are enabled?