Relates to MC-278216 and MC-278220.

The bug

The tab character U+0009 most often appears as a large space, often the width of four U+0020 spaces. However, in Minecraft, it appears as a control character.

How to reproduce

For some reason this character cannot be pasted into the game at all, so we will need to force it to appear using a command:

/tellraw @p {"text": "a\u0009b"}

Expected results

A large gap between a and b.

Actual results

It appears like a control character.