I think learning to master one element at a time like br and P is useful

Though there are many elements that create "Links" to do this all at once might confuse you unless you are in a college class that is teaching you this or a high school class teaching you this. You need to have someone who "KNOWS" to ask questions of otherwise all this is going to get very confusing.

It's sort of like learning to drive a car without any help which can be dangerous in various ways. Even though learning to program in HTML is unlikely to cause your death (at least not at first) depending upon where you live on earth it is good to have a teacher that knows the ins and outs of what is actually going on as you learn this stuff.

For example, by watching a Youtube video about driving a car you might master it eventually even without a license as long as you don't kill or injure anyone including yourself. But, then there are things like if you don't know to put gas in the gas tank (or diesel in the diesel tank) on some vehicles eventually you are going to run out of what powers the vehicle if you don't know to do this.

Likewise if you hit a rock on your oil pan and all the oil runs out your engine is going to freeze up soon and it will be useless to anyone ever again likely because the cylindars will warp the rings might break and the valves might break off inside the engine and in the worst case your crankshaft could explode along with the whole engine and kill you depending upon which direction all the parts go when the engine blows up when it freezes at about 70 or 80 mph. By the way if this happens put your car or truck in neutral and you might survive this.

There are similar problems if you don't program things correctly in the first place in regard to computers.

So, usually programmers (Debug) their software and look for mistakes before they put it into place (most of the time if they are smart) and don't want to be legally liable for any problems they create.

Note:
However, I suppose if you just use the "compose" mode at blogger.com (Blogspot) where this originates the only problems you might create would be in HTTPS which I believe is what Facebook uses for security. For some reason or other when you run a quoted part (from another article) through the automatic coders from Blobspot or other blogging sites it can cause problems there.

However, my thought is that Facebook actually does this only to end the competition of sites like Blogspot and others to force people into a format that excludes all Google, and Yahoo and other blog sites communication in order to legally put in jeapordy other competetive sites. This is the way the biggest Internet companies have always operated.

However, this is completely unfair to the majority of Internet users in every single way worldwide.

So, these kinds of actions by all the biggest companies on the Internet only causes more and more monopolies online worldwide and excludes more and more basic important communications worldwide regarding the majority of internet users worldwide.

So, these kinds of monopolistic undemocratic kinds of methods by monopolizing companies likely will one day end the internet completely or make is so draconian than no one other than governments use it ever at all worldwide.

You and I can already see this coming in the near or far future just from what Putin and Russia have done to democratic elections in the U.S. and Europe already through various insidious means by using the Internet already.