I heard that Counterparty cannot handle lock time, but I cannot understand why.
What will happen when we use nLockTime in a transaction which includes Counterparty transactions?
Disclosure: I work for Coinprism.
Counterparty uses the Blockchain for timestamping only. It doesn't use it as a ledger since it builds it's own "parallel" ledger.
As a result most advanced functionality of the Bitcoin ledger can't work on Counterparty:
If you want to be able to use all bitcoin features out of the box, you need to look at colored coins.
nLockTime can in fact be used by meta-protocols (e.g. Counterparty, Mastercoin) because nLockTime simply decides when a transaction can be mined.
The first "answer" didn't explain why nLockTime can't work (too superficial), and it also claims without substantiating it that Payment Channels can't work although Storj is working on a payment channels implementation for Counterparty and you can run it on testnet today: https://github.com/F483/picopayments-cli-python#testing-guide. (There's a separate repo for the hub, for those who want to run a hub.)
I would say it's more likely than not that Counterparty will be able to work with nLockTime (if a transaction can't be mined, it can be ignored by Counterparty until after it can).