Unseen, but Hidden in Plain Sight

Question

This riddle has a single, one word answer, with an explanation as to how you found it. You may be able to make a good, or even correct, guess from just the contents of the poem below, but if you've solved it in the way I intend, you will know without a doubt.

The answer to this riddle
Is hidden in plain sight,
Though you may need to fiddle,
To solve the question right.

I'm something that you never see,
At least not at a glance,
Though if you poke around in C,
You often get the chance.

Alone, on *Nix, I shall suffice,
In my purpose I'll succeed,
But Win's a world, cold as ice,
I need a coachman to proceed.

You use me many times each day,
Though perhaps you didn't know,
You make me in a different way,
When at home or on the go.

Answer 1

The answer is:

newline

The answer to this riddle
Is hidden in plain sight,
Though you may need to fiddle,
To solve the question right.

This has double meaning:
1. To look at the source of the question for clues
2. The newline is hidden in plain sight of the poem's structure

I'm something that you never see,
At least not at a glance,
Though if you poke around in C,
You often get the chance.

We don't really see whitespace such as newlines. In C, you could see the newline character encoded as '\n'.

Alone, on *Nix, I shall suffice,
In my purpose I'll succeed,
But Win's a world, cold as ice,
I need a coachman to proceed.

In Linux/Unix, a text line ending is encoded as '\n' (line feed), while in Windows, a carriage return is added, resulting in '\r\n'.

You use me many times each day,
Though perhaps you didn't know,
You make me in a different way,
When at home or on the go.

When working with a word processor/text editor, pressing enter adds a newline.

How I arrived at this specific word:

The first and second verses give strong clues to look into the source. Looking into the edit of the answer yields some hidden information.
1. Congrats_you_found_the_hidden_clue/now_our_friend_morse_will_see_you_through
2. This_last_line_doesn't_add_that_much/just_there_for_rhyme_and_beat_and_such

In addition you can find
1. Lines starting with [][1] or [][2]
2. Lines ending with <br> or '  ' (two spaces)

Interpreting the whole thing as a morse code puzzle, I tried using [][1] as the start of a new character, <br> as a dash, and '  ' (two spaces) as a dot. Reading through the poem linearly spells out:

-. . .-- .-.. .. -. . (newline).

Credit goes to pacoverflow for doing much of the heavy lifting.

Answer 2

The answer is:

linefeed

The answer to this riddle Is hidden in plain sight,

You have to edit it to see hidden formatting and a couple of hints:
1. Congrats_you_found_the_hidden_clue/now_our_friend_morse_will_see_you_through
2. This_last_line_doesn't_add_that_much/just_there_for_rhyme_and_beat_and_such

Though you may need to fiddle, To solve the question right.

There are some mistakes, that I will point out later.

I'm something that you never see, At least not at a glance,

LF, or linefeed, is a special character in computing that represents a newline. You don't actually see that character on the screen (at least not "LF" on the screen).

Though if you poke around in C, You often get the chance.

You can "see" the LF character by inspecting strings in code using C or other programming languages. LF has ASCII value 10.

Alone, on *Nix, I shall suffice, In my purpose I'll succeed,

On Unix/Linux systems, LF is the only character required to specify a newline.

But Win's a world, cold as ice, I need a coachman to proceed.

Windows systems require the CR (carriage return) in addition to the LF.

You use me many times each day, Though perhaps you didn't know, You make me in a different way,

People press Enter to make a newline many times a day, but they might not realize they are specifying the special LF (and possibly CR) character in doing so.

How I found out the answer:

When editing the question, and seeing brackets in front of certain lines, and <br> after certain lines, I took the hint about Morse to mean that either:
* each line with brackets in front of it represents a dot, and each line without brackets in front of it represents a dash
* each line with <br> after it represents a dot, and each line without <br> after it represents a dash

So the first stanza represents L in Morse code (using the brackets), the second stanza represents F (using the trailing <br>s), and the fourth stanza represents R (using the brackets; remember the second hint that the last line doesn't matter).

One line said you "need to fiddle". The third stanza represents Q in Morse code (using the brackets), but should be changed to have no brackets before the first line, brackets before the second line, no brackets before the third line, and brackets before the fourth line, so that it represents C.

The stanzas spell out LFCR in Morse code.