I agree that out Foreign Ministry officials are not following internationally accepted protocols.
From the time I know when an election is over our president or priminister always visits India. But this does not happen when there is a new Indian PM is appointed. These are our faults.
As to address of people there is no prohibition if there are considerable number of people from the country. Normally there are no considerable number and they host a dinner and a speech is made. But if there are considerable number of Indians eg Sri Lanka, Fiji, and other places where indentured labours were taken from India the visiting head can speak to their people but this needs an approval. Soon after elections Modi visited Fiji and had a massive open rally in the capital. So it seems that he like this kind of things!
Recently there was a Diplomatic raw between Trukey and Denmark as the Foreign Minister of Turkey wanted to come to Denmark to address their people regarding the elections they just had and the Denmark refused, so these are issues for professional people to handle professionally.
It is sad that we lack professionalism in all fields including in Diplomacy.