I don't see a reason why smart or curly quotes should affect posting characters.

For chars in the ANSI range, you just hold down the Alt key and type the decimal number of the character on the Number Pad (NumPad must be turned on.)

128 is the decimal number used on US machines for the euro, so if you type Alt-0128 you should get €.

For characters in any range, you can use the decimal number for the character and type:

&#nnnn; where nnnn is the decimal number.

Entered this way, € produces €.

For characters in any range, you can use the hex number and type:

&#Xnnnn; where nnnn is the hex number.

You used hex number 20AC for the euro, so typing € gets €.

For some characters there are character names, and you can type ® to get ®, © to get © and such, but no quotes of any kind are needed.

Have you found a harder way to do it?

John