===Another proposed rewrite=== 

 The present version (ie, without the example) reads: "Some Commonwealth parliamentary systems combine a body of written constitutional law, unwritten constitutional precedent, Orders in Council, letters patent, etc. that may give a head of state or their representative additional powers in unexpected circumstances." This is unclear. 
 *Is it saying: only some do, but others do not? 
 *Is it saying that there are some Commonwealth republics in which the head of state has a "representative" of like status to a realm's governor-general? 

 Would it not be clearer to begin: Commonwealth parliamentary systems, whether realms or republics, combine a body of written constitutional law and unwritten constitutional precedent that may give the head of state, or a governor-general in a Commonwealth realm, additional powers in unexpected circumstances ... (then let the example be added) ...'', such as when Governor-General of Australia Sir John Kerr in 1975 unilaterally (that is, without direction from ministers, parliament, or the monarch) dismissed Australian Prime Minister Gough Whitlam in order to break a stalemate between the House of Representatives and Senate over money bills."