This is fun but I do wish papers would stop using "obvious" or "not difficult" so frequently. This paper has five uses of "obvious," 3 uses of "clear" or "clearly," a "should not be difficult," a "what can possibly be simpler?," and a "It is difficult to imagine that this algorithm was not discovered before."
Is this a particularly complex algorithm or proof? No. But it reads like the author was terrified that someone would be able to understand their paper simply by reading it once and worried that would make the author look dumb. That's backwards, though. Easy to understand concepts are a good thing.
Of the five "obvious" words, two of them are used to say that something is not obvious and your last two examples are something entirely different. The uses here seem quite reasonable. But these words should be helpful, not insulting! If it's not clear, as the author claims, then you've likely misunderstood something. No point pondering it for twenty minutes, better go back and reread the statement first.
But of course they do get misused and there's not much more demoralizing than getting stuck on something 'obvious.'
Plus I completely dislike the title. These kind of papers treat arxiv as if it is discussion group. It is not. It is paper repository for things that has been written with lot of care and thought.
Is this a particularly complex algorithm or proof? No. But it reads like the author was terrified that someone would be able to understand their paper simply by reading it once and worried that would make the author look dumb. That's backwards, though. Easy to understand concepts are a good thing.