It is widely known for example that hammers have been used since before recorded history. We only know this because of archaeological finds. There are no documents. Still, many people have applied for and received rights to specific types of hammers for specific uses.
Such rights are usually no problem to others since it is a simple matter to make a hammer equally different from that one as it is from all others before it. Essentially then, no one owns the basic idea of a hammer, but the tack hammer of one particular inventor might work especially well putting a particular tack in a particular type of wood.
A question arises what hammer is best for other tacks and types of wood. An argument might develop when a new tacking job is found. Who should get the rights to the hammer for that job? Several people might solve the problem independently. The new design might be quite common sense. In that case no one might get the rights because being first is not enough. To get rights a new device must solve a "longstanding" need for it to be eligible in the patent laws of some areas. Being one day ahead of someone working entirely independently doesn't count. Not everyone agrees. Some people think the "first" occurrence has some special right that must be protected. Who owns the hammer might be moot if it only works better on the boat someone else invented. No one else needs the hammer and the inventor of the hammer can't build the boat if he needs the permission of boat's inventor.
Perhaps you can see at this point how the arguing might never end however useless and vain.
Examples of the problem whether the "first" occurrence is special are quite numerous well before computers came along. Quite many new problems arrived with computers though.
One problem computers significantly reduced concerns colors. Computers can paint a complete list of colors to the extent that people's eyes won't be able to detect any difference in any "new" color after that. That is essentially a catalog of "all" the colors there could possibly be. The "ownership" of colors was not really a big problem before. The Navy never claimed much ownership of "navy blue" for example.
An issue brought about by computers and still found today concerns data compression. There are several types of data compression with various uses, much like there are many tack hammers. The difference between data compression and the simple use of variables to compact or represent data never seemed worthy of independent rights. People were using variables before computers. The basic idea of compression is therefore essentially public property. Yet, you will find that in order to decompress or display some compressed data you might need a licensed copy of the program for that particular style of compression. If you don't like being bound by that requirement there are conversion programs that have the rights to that type and another type you might find less obtrusive in the future. You can make a copy in the other style.
Others things on computers seemed "new" to many people that were considered "common sense" by many others.
The United States Copyright Office made rules to deal with the problems that might occur in the future. Unfortuitously not everyone understands the problems and not everyone understands the rules. Misused, the rules can be another problem themselves. Not even everyone at the copyright office agrees on the interpretation of the rules.
Particularly troublesome is the notion that if something cannot be copyrighted then it cannot be credited either. It is not necessary and leads to trouble. When no one can take credit for making the right choices then the wrong choices flourish. For example the method of indicating a new paragraph used on this page is preferred by most print publishers. The method used on too many websites was an accommodation to early computers that communicated by line printers. While it might seem stylish for web pages to mimic line printers, there are no line printers that can read pages. They would print out the source page with markup mixed in which, would not be very easy to read.
When I copyright an article I want it known that I prefer the style of indicating paragraphs preferred by print publishers. It does not mean that I want to own something that cannot be owned. I want credit for using that style in my work, not for others using it in theirs.
To be deserve a copyright you must deserve credit, however it does not follow that to deserve credit you must deserve a copyright. Confusion over the difference is the reason so many web pages use the "wrong" style. When government removes responsibility then things don't get done correctly. The blind follow the blind without knowing where they are going or why.
If some had wondered if my copyright covers any and all of the few possible methods for indicating a new paragraph why would I need to pick a preferred one, now they should know. It is because it is the better way for this text.
I agree with the Copyright Office that no one owns this style of paragraphing. There are not many different possibilities and they have all been used for centuries. Anyone who has had to express himself in 700 words or more on an issue appreciates the usefulness of this style of breaking it up. It is common sense in so far as writing 700 words on an issue is common.
The choices of various colors and sizes in printing, the various arrangements of text with other stories, in fact all the elements of page design are important, especially in newspapers and magazines. Someone deserves credit for making those choices. There is no danger that will limit others from making similar choices, colors, sizes, and so on.
People who write music might have a similar problem selecting instruments to best perform your songs. If your copyright is for the song performed on any instrument that can play your notes, then why select? Does it mean you want to own all use of that instrument? Does it mean you don't want to own your song played on other instruments? I am not aware of any ownership of the "conventional" idea of how particular instruments sound. If you own a MIDI player it probably uses a "conventional" sound of, for example, a trombone. I believe if you prefer your song be played on a "trombone," or some conventional idea of it, you can without considering the inventor of the sackbut or worrying about people playing your song on a piano without giving you credit.
If common sense is not so "common" as many have said, then perhaps it is understandable how fiercely some people defend their use of it.
I will apply for a copyright of this page if necessary. I will claim "credit" for the design of it. If the person assigned to the case (Not all of them disagree with me.) says I must remove any "claims" to page design I will argue. I can remove any claims to "copyright" of the page design they imagine, but not "credit" for the page design which, as explained in detail here, is a different thing.
If they still don't understand, then we go to the courts, but I doubt that will be necessary after writing this. There are other options too. Musicians might use older recording devices like magnetic tape. Journalists might photograph their pages and copyright them as "visual arts." That way they won't get confused by the computers.