English idioms are acceptable in informal communication! In my opinion
And it's fine to have that opinion. However, not everyone else does. Personally, my opinion is that unless it was said intentionally, it should be said intelligently.
For example, take the 'word' irregardless. It's even in Microsoft's spelling dictionaries. People commonly misuse it to mean 'without regard'. Yet the word irregardless is a double-negative. Regardless is the <i>proper</i> word for 'without regard'. <i>Ir</i>regardless is the negation of 'regardless'. So anyone who says irregardless is actually saying that they do regard.
It's just one of those words that people throw around without thinking and only makes them sound stupid. If people <i>want</i> to sound stupid, I won't stop them. I might inform them of their mistake, but I certainly won't <i>force</i> them to use that grey fleshy thing between their ears. My opinion is that stupid is as stupid does. If you sound like a moron, then you just might be one. (Why do I feel like this is an intro to 'You might be a redneck if...'?)
The only exception is, of course, when done intentionally for humor.
"<i>Yeah, if you treat them like equals, it'll only encourage them to think they <b>ARE</b> your equals.</i>" - Thief from <A HREF="http://www.nuklearpower.com/daily.php?date=030603" target="_new">8-Bit Theater</A>