You can change the default comment on a trade (MT4, MT5, and cTrader only). FXCM and LMAX don't support this function. 

The Comment feature is usually used to know which Master placed the order on a Slave account. To do that, you can enter a comment by going to your Master's advanced copy settings. 

You can define a comment for each master/slave copy link, the comment will appear on the slave trade.

Please note that it is not possible to copy the comment defined on your Master trading platform directly. Duplikium's "Comment" feature only applies to the comment entered on your Trade Copier. 

Please note that the comment feature is available only for accounts with a Subscription Plan.