Semicolon is not a valid character for use in Tag values

[mbokman]

When you want to apply custom creation or retention parameters to an instance, you are directed to separate the four possible custom parameters by the semicolon character.

According to the documented EC2 Tag restrictions, the semicolon is not a generally allowed character and I am not able to use it when entering it as part of a Tag value in an Opsworks Layer, neither in the AWS Console, nor via CloudFormation.