First, allow me to say thank you for SortPom.

The conscious choice of 2 * indent + 1 space as a continuation indent seems to me an unusual one. In practice, I've only ever seen 2 * indent or 1 * indent continuation indents, no matter whether the indents are spaces or tabs. For that reason, how do you feel about standardizing on 2 * indent as the continuation indent? Considering there's necessarily always a line separator before any continuation indent, that line separator alone substitutes for space as the obligatory whitespace between attributes, even when the indent is 0.