How allow moderators to give a rebuke to user I'd like to allow moderators to give a rebuke for users. If user has e.g. 3 rebukes, the account of user should be removed or blocked - automatically or moderator should be inform about it.
You can use Flag module for that. You can set flag for users or posts created by users or something else as per your requirement.

Use rules to set rule on flagging &amp; their counter value. There is very nice tutorial series on flag here by Johan Falk. You can see his rules tutorials to have better understanding about setting rules based on flagging.