Why my laptop sends ARP request to itself?

This behavior is a very good way of finding a potential duplicate IP.

If your computer gets no answer, then it is the only one with that IP. If your computer gets an answer, there is another computer with the same IP which is a problem obviously.

Concerning RFCs, I find them horrible to read. I only use them for reference concerning specific problems. I have probably read just one from start to finish. The rest I read bits by bits. IMO, I find that the best way to learn about something is to pick up the O'Reilly or similar paper book and read it.

There can be more then one RFC for a single protocol. For example IPv6 has 10 different RFC just concerning transition mechanisms from IPv4 to v6. There are many others for such things as neighbor discovery. SCTP is covered by 4 RFC also.

This is standard behavior to prevent IP conflicts. It is dicussed in RFC 5227 IPv4 Address Conflict Detection. It also allows routers and neighbors to update their ARP tables so they can communicate with your computer.

By asking who has an IP address it is possible to determine if the IP address is in use. This allows the computer to at least log the existence of a conflict if one exists.

It is this mechanism that allows a computer to use automatic IP address configuration to work using the 169.254.0.0/16 address block. Computers generate an address in this range, and then use APR to see if it available. If not they try other addresses until they find one available. As the networks are usually small and the address range covers over 65000 addresses, they can find an address quickly.

The arpwatch utility builds a database based on the arp messages which can be used to notify administrators if address are in conflict, or are being moved to new hardware.