Scoreboard objective/teams/tags don't support certain characters when testing for scores/teams/tags in selectors

*Info: maybe contains some of this:
MC-51960

When you create a scoreboard objective, called for example:

/scoreboard objectives add Game.2.Points dummy

It works perfectly, even when you do:

/scoreboard players set @p Game.2.Points 1

But when you try:

/testfor @a[score_Game.2.Points=1]

it won't work.
The same is with all signs which aren't letters (exepct "§")