First off I want to say I'm aware this may sound like a feature request, but even though the game is working as intended, this is a very long running issue caused by a small oversight.
The problem is Italian keyboards lack the tilde key (as you can see in this image), indispensable for entering relative coordinates when writing commands.
Up until recently I didn't mind it too much since I only use commands occasionally, but then I realized this issue might be a big annoyance for other Italian players who are a lot into this part of the game.
My current workaround is to use Windows' hotkey to swap keyboard layout to English, enter the ~ character and switch back to Italian, but even then, it's 6 or 7 keystrokes just to enter 3 characters. I'm "lucky" enough to know about this method, but I'm sure a lot of people don't and have to go through copy the symbol from elsewhere out of the game and paste it in every time they are working with commands. Easy to see how tedious it can get.
Changing OS settings or even having to alt-tab out of the game in order to use a game feature seems very odd and out of place to me.
The best solution I thought of is having an additional symbol for relative coordinates (perhaps ^) without altering the current syntax everybody is used to. This way you can make Italian players happy without negatively affecting the rest of the userbase. Win-win.
Summary of the bug:
What I expected to happen was...:
I was able to use command features without the aid software external to the game.
What actually happened was...:
I was unable to enter relative coordinates because my keyboard is missing the ~ key.
Steps to Reproduce:
1. Go in your OS settings and change keyboard input language to Italian.
2. Enter the command /tp ~10 ~20 ~30
.
3. Find yourself unable to type ~.
Linked issues
Comments


Still an issue in 1.8.7, and again, I don't think this is a duplicate of MC-68642. In fact, MC-68642 was fixed while this is still occouring.
Although they sound similar, MC-68642 is about keyboard inputs not being interpreted correctly, while this report instead is about the game expecting me to type a character not existing on my keyboard at all.

6 months have gone by and this is still marked as a duplicate despite it not having anything to do with MC-68642.
If my description isn't clear enough then just say it, I'd be happy to try to word it better and more in details.

This is a feature request, and thus should be posted on the Minecraft Suggestions subreddit, not here. I agree that there's a usability issue, but that's the fault of whoever designed a keyboard layout without commonly used symbols that are in the basic ASCII character set. Just because they are not common in Italian is no reason to assume that the user will not need them when interacting with the rest of the world. The tilde character is commonly used in mathematics, logic, programming languages, web urls, and directory or file names in various operating systems. Minecraft can no more be expected to accommodate such shortsightedness than any other software used in those contexts.
The standard Linux and Mac Italian keyboard layouts include AltGr combinations for the tilde, amongst other useful characters, by default. On Windows, there are several workarounds available beyond the obvious copy+paste or temporarily switching keyboard layouts. They can easily be found by searching the internet for "type tilde on italian keyboard". You could use the alt-code (alt+126), use the more sensible "Italian (142)" keyboard layout which changes the AltGr combinations and includes tilde, or map a key for it yourself using the Microsoft Keyboard Layout Creator.

Thank you for the reminder about the Minecraft Suggestions subreddit, at the time of creating this report I opted for the bug-tracker because that subreddit was not getting much attention from the developers, but things seem to have improved since then, so I'll probably post my request there as suggested.
Still an issue in 1.8.4, and I don't think this bug is a duplicate of, nor relates to, MC-68642.