User mode commands can be more concise
If multiple users are selected for a mode change, the commands should be concatenated for brevity's sake, since issuing individual mode commands for each selected user can sometimes be a very lengthy task.
The RPL_ISUPPORT header sent by the server defines MODES=x, where x is the number of mode changes allowed per line. Mode commands can be stacked up to that limit either as
/mode #channel +o user1 +v user2 -h user3 [...]or
/mode #channel +ov-h user1 user2 user3
A quick glance at SearchIRC's biggest servers list indicates most networks support at least 6, although a few (freenode, efnet, abjects) don't list a MODES= value.