Stop yapping unnecessarily
Yes if it becomes white noise. However it is largely a matter of style in many cases. Tony Spreadbury and Chris White were quite different in this respect, but both were top class referees and would surely have been worse if each had adopted the other one's style.
Talk to the press
This was tried in South Africa, when the referee was required to be at post match press conferences. After the novelty wore off, and journalists found that referees could explain the reasons for their decisions, the press apparently lost interest.
I have no fundamental problem with the idea, but there is a danger of it being used solely to attack the referees.
Learn the lingo
I think this is a really bad idea.
I always had a high regard for Chris White as a referee, and he used to referee using some French phrases – and made mistakes. A crucial one was shouting "Lâchez, rouge" when refereeing Munster against a French team. How many Munster players realized he was talking to them? It is typical of what happens when you know some phrases but do not speak the language. It is also only too easy to pick the wrong phrase on the spur on the moment. As an experienced linguist, I have been there and done that.
Trying to put the language burden on the referee is a non-starter once you stop to consider the problem. At this RWC we have had the following languages to deal with: French, Japanese, Spanish, Georgian/Russian. Romanian, Italian. 13 of the countries could be regarded as English speaking. French and Italian may seem to make sense for the 6N, but why single them out for a World Cup? 3 matches (Group B) involved teams speaking none of those languages:
The only practical solution is to say that in internationals, unless the referee and both teams have a common language, play in the game shall be refereed using a subset of English phrases as published by the IRB. At a stoppage other possibilities arise, but there is no time pressure then.
The result of that would be that all countries would expect to be refereed in that way at some stage, so they would put in the effort to ensure their players would recognize the phrases eg by refereeing like that just below international level. Passive understanding is much easier than active use.
It would put a small burden on non-English speaking referees, but at least it would only relate to learning one language – and it is pretty well what they have to do already. Some are not very good at it (Berdos) which just shows you cannot expect a top class referee also to be a good linguist.