Via a command block set and activate the command: "/gamerule commandBlockOutput false". Normally this gamerule will make it so commands are not displayed when activated via command blocks. However if you set another command block to have a gamerule command, (ex. /gamerule doFireTick true), the command will still that you set that command.
MC-6060
Command Block Gamerule Update Problem
Resolved
Fixed
2
(Unassigned)
Community Consensus
command_block, gamerule
Minecraft 1.4.6, Minecraft 1.4.7, Snapshot 13w01a, Snapshot 13w01b, Snapshot 13w02a, Snapshot 13w02b
Minecraft 1.5
Retrieved
I can confirm this, but the description is a bit confusing. Do you mean "the command will still show" at the end?