I meant Ireland in the same context as you used ROI - I was told earlier in thread that it was 'Ireland' not 'ROI'.
I have no comment to make on the discussion upthread, but in the context you used it, 'Ireland' was the wrong phrase to use. Because the island of Ireland includes ROI and NI, and NI is not an entirely separate country to the rest of the UK. ROI, however, is. For better or for worse.
As for the rest, you can only take that semantics, words mean different things to different people argument so far. If you're going to do that with hard border, it will become as meaningless as Brexit means Brexit.
Lastly, you would probably benefit from some research on what the current situation is. Ferries between Britain and Ireland, either side of the border, don't involve passport checks. This has been said already. People can and do travel illegally between the two that way. It becomes even more of an issue when a group of people living in ROI, EEA nationals, don't have the automatic right to be in the UK, because it creates a bigger group of people who could live illegally in the UK. This is obviously going to be of concern to people who voted Leave because they thought it would mean full control of UK borders. The question is, where they come in the wish fulfilment priority list.