[DobbysGamertag]

pawn Код:

COMMAND:ban(playerid,params[])
{
    new reason,string[124];
    //other stuff
    format(string,sizeof(string),"%s",reason);
   INI_WriteString(filenamehere,"Ban Reason",string);
}

That should write into file with a reason. I've put filenamehere as that because i use

pawn Код:

new INI:file = INI_Open(Path(playerid));

So it'll write into my player files as

pawn Код:

COMMAND:ban(playerid,params[])
{
    new reason,string[124];
    //other stuff
    format(string,sizeof(string),"%s",reason);
    new INI:file = INI_Open(Path(playerid));
    INI_WriteString(file,"Ban Reason",string);
    INI_Close(file)
}

Or you can be lazy and write it to a log. You can then look through logs and see sorry if it seems messy. I can't script from the reply box :P