The Commentary System is a special feature introduced in Half-Life 2: Lost Coast which allows DVD-like director's commentary to be embedded inside levels. In most games, users enable commentary mode through a "Developer Commentary" menu which launches levels with commentary enabled.

To enable community commentary you will have to copy two sets of files from Half-Life 2: Update folder to Half-Life 2: Mmod folder. First go to steamappscommonHalf-Life 2 Updatehl2maps and copy all txt files named like this: d1_canals_10_commentary.txt (these are names of HL2 maps followed by "_commentary").