Some writers think that the standard rules of capitalization can be ignored if the situation calls for it. I don't think they can, and the situation never calls for it.
As a writer, you are trying to effectively communicate with your reader(s). Obfuscating your meaning by eschewing the standard is distracting to the reader, and it makes it mechanically difficult to read what may already be a literarily difficult piece. If your writing is difficult to parse, the chances of your audience actually reading it decline. If your writing is too difficult, it won't be read at all — by anybody.
This concept applies to other disciplines as well. QWERTY keyboards continue to be made and sold today. Why? It's what people expect, understand, and know. Related to writing, serif fonts tend to be used because they are easier to read (when presented at the standard of 12pt) for extended periods of time¹. Could you use Arial anyway? Sure, but why inconveneince the reader? Mechanics and meaning are separate entities, and they should be treated as such.
To return to the subject of capitalization, it is important to use mechanics with which your reader is familiar. Capitalizing "I" may seem unimportant to you, but it catches me off guard every time I see "i" in a sentence. I don't necessarily think that "I" am more important than "you;" I just happen to have become accustomed to the way things are done†. The same goes for capitalizing proper nouns and the first words of sentences. They serve to alert the reader that there is something different about that word. The first capital of a sentence reinforces the sentence break, and the capitalization of proper nouns demonstrates that not all airports are Chicago O'Hare International Airport, etc..
It is completely possible to communicate complex ideas while adhering to the established rules. If you feel that you genuinely need to break the rules to make your point, I argue that your writing isn't strong enough.
So you've got an original idea or an outstanding story to relate to me? Your ideas are just as original when properly capitalized. Delivering a speech at a near-inaudible volume level doesn't make your ideas more profound. It makes them harder to take in. The same idea applies to capitalization. Allow me to understand your words so that I can attempt to understand your ideas.
Thank you.
† Similarly, seeing "Ich" in the middle of a German sentence would catch me off guard, as well.
References
- Typography: serif vs. sans-serif, Frank Ates, http://kurafire.net/log/archive/2005/07/23/typography-serif-vs-sans-serif