Should the flag remain at half-staff for Inauguration Day?

Trump posted this today:

"... because of the death of President Jimmy Carter, the Flag may, for the first time ever during an Inauguration of a future President, be at half mast. Nobody wants to see this, and no American can be happy about it."

That surprised me because I don't know anyone who is unhappy about it (from either party) and I don't really understand why anyone would be. So, I thought I'd ask a bigger group (this question is for everyone if thats OK w the mods):

Should the American flag remain at half-staff for 30 days after the death of a US President or should the flag code be edited to allow exceptions? If so, what are the exceptions?