Affects : Probably anything after which a bracket of any kind can be used, without adding a space first. Such as blocks in /setblock, /fill and /clone, items in /give, /clear and /replaceitem, and target selectors (that's everything I noticed, but there may be things I missed).

After tab-completing an argument (like /setblock ~ ~ ~ furna [TAB]), the bracket suggestions do not appear like they would if it was typed out manually. This also applies to the selector suggestions, e.g. (/kill @a[gamemode=survi [TAB])