I structure my accounts such that different sub-accounts contain only a single commodity. So, for instance, Assets:Cash:INR and Assets:Cash:USD, and so on.
When I have a transaction with postings having multiple commodities (for instance, if I have a single transaction involving purchases in both INR and USD, the auto-suggested default amounts (i.e., the amounts if I simply press "Enter"/"Return") would be applied to a single account, whereas I would usually have two separate accounts to which they ought to be applied (i.e., Assets:Cash:INR and Assets:Cash:USD, rather then both the INR and USD balances from a single account).
If hledger-iadd could be smarter about which commodity to apply to which account (e.g., by checking if past transactions to that account only involve a single commodity), that would be very helpful. Currently, I have to manually enter the commodity and the amount instead of using the default auto-suggestions.