You can, especially when you have at least 1 sMerit. See this section: https://bitcointalk.org/index.php?action=merit. Every time you get 2 merit, then you can spend 1 sMerit for other users.

50 merit/ user within 30 days. This means if you have 1000 sMerit then you can spend it on 20 different users.

There is no limit to the amount you receive if it comes from different users. The rule is that you can only receive and send 50 merit in 30 days from or to different users. This cycle will repeat for the next month, and I think that's how the system works.