@cfrank Yeah, there's always the incentive not to vote for a preferred candidate in PR for the reasons you give.
With the monotonicity, Phragmén is not actually non-monotonic as I say, but only weakly monotonic. E.g. with 2 to elect:
100 voters: ABC
100 voters: ABD
Phragmén methods tend to be indifferent between AB and CD (unless modified in some way), and that leaves them open to:
99 voters: ABC
99 voters: ABD
1 voter: C
1 voter: D
Where CD would be preferred. Electing in a greedy sequential manner rather than optimally would actually lead to more monotonic results in these cases, but other examples can be found.