Dealing with the signature position and the signature itself is only necessary if we actually want to include a (non-empty) signature. I propose something like:

```java
boolean useSignature = ...
if (useSignature) {
    textBodyBuilder.setAppendSignature(true);
    textBodyBuilder.setSignature(signature);
    textBodyBuilder.setSignatureBeforeQuotedText(mAccount.isSignatureBeforeQuotedText());
} else {
    textBodyBuilder.setAppendSignature(false);
}