[ClassicHopper]

Trying to get rid of "[SM] Console: Changed cvar "sv_cheats" to "0"" for example.
Huge blob of code below, skip past for a part of which I assume is more accurate.

public Action:Command_Cvar(client, args)
{
	if (args < 1)
	{
		if (client)
		{
			ReplyToCommand(client, "[SM] Usage: sm_cvar  [value]");
		}
		else
		{
			ReplyToCommand(client, "[SM] Usage: sm_cvar  [value]");
		}
		return Action:3;
	}
	new String:cvarname[64];
	GetCmdArg(1, cvarname, 64);
	new var1;
	if (client && .2920.StrEqual(cvarname, "protect", true))
	{
		if (args < 2)
		{
			ReplyToCommand(client, "[SM] Usage: sm_cvar  ");
			return Action:3;
		}
		GetCmdArg(2, cvarname, 64);
		.17740.ProtectVar(cvarname);
		ReplyToCommand(client, "[SM] %t", "Cvar is now protected", cvarname);
		return Action:3;
	}
	new ConVar:hndl = FindConVar(cvarname);
	if (hndl)
	{
		if (!.17872.IsClientAllowedToChangeCvar(client, cvarname))
		{
			ReplyToCommand(client, "[SM] %t", "No access to cvar");
			return Action:3;
		}
		new String:value[256];
		if (args < 2)
		{
			ConVar.GetString(hndl, value, 255);
			ReplyToCommand(client, "[SM] %t", "Value of cvar", cvarname, value);
			return Action:3;
		}
		GetCmdArg(2, value, 255);
		new var2;
		if (.2920.StrEqual(cvarname, "servercfgfile", false) || .2920.StrEqual(cvarname, "lservercfgfile", false))
		{
			new pos = StrContains(value, ";", true);
			if (pos != -1)
			{
				value[pos] = MissingTAG:0;
			}
		}
		if (ConVar.Flags.get(hndl) & 32 != 32)
		{
			ShowActivity2(client, "[SM] ", "%t", "Cvar changed", cvarname, value);
		}
		else
		{
			ReplyToCommand(client, "[SM] %t", "Cvar changed", cvarname, value);
		}
		LogAction(client, -1, "\"%L\" changed cvar (cvar \"%s\") (value \"%s\")", client, cvarname, value);
		ConVar.SetString(hndl, value, true, false);
		return Action:3;
	}
	ReplyToCommand(client, "[SM] %t", "Unable to find cvar", cvarname);
	return Action:3;
}

where I'm focusing

		if (ConVar.Flags.get(hndl) & 32 != 32)
		{
			ShowActivity2(client, "[SM] ", "%t", "Cvar changed", cvarname, value);
		}
		else
		{
			ReplyToCommand(client, "[SM] %t", "Cvar changed", cvarname, value);
		}
		LogAction(client, -1, "\"%L\" changed cvar (cvar \"%s\") (value \"%s\")", client, cvarname, value);
		ConVar.SetString(hndl, value, true, false);
		return Action:3;
	}
	ReplyToCommand(client, "[SM] %t", "Unable to find cvar", cvarname);
	return Action:3;
}

Do I only remove \/?

LogAction(client, -1, "\"%L\" changed cvar (cvar \"%s\") (value \"%s\")", client, cvarname, value);

[Powerlord]

...you do know that the basecommands source is shipped with SourceMod and you didn't have to decompile it to get said source code, right?

Edit:

Anyway, to answer the question, just modify cfg/sourcemod/sourcemod.cfg and change the sm_show_activity setting to control what you want players to see.