::::::::: Use or indeed overuse of the words 'informer' or 'suspected informer' alone remains pejorative and inappropriate here. Angus's suggestion of "suspected by the IRA of being an informer' is not unreasonable as it indicates that it is a concept or crime particular to that side of the dispute. 
Sarah argues, "What they are commonly called is what we should reflect here. Any inhabitant of Ireland who assisted with information given to the British was an informer." She avoids my earlier point. 'Commonly' has to include, in Ireland, Protestants and Unionists (who were themselves British) and therefore the concept is not common currency unless you regard Protestants as people of no consequence at all in the matter. Can you inform yourself?
And was it in 'common' use in Ireland that you would call someone who had reported a rape or a stray cow an informer? 
Sarah's other point that "Protestants who openly supported the Republic were never killed. So it wasn't a sectarian matter" is risible. As if you execute those who come across to your side? Anyway most Protestant Republicans became Catholics. 
The number of Protestants in Cork who were home rulers would have been tiny and the percentage who supported the separatists minute and can pretty well all be named like Miss Dorothy Stopford or Sam Maguire. 
I will go for Angus's phrasing in my next edit.