Pleats or no pleats for modern looking suits?

Definitely no pleats considering what you are looking for.

If you want the columnar look shown recently in men's magazines, then no pleats. However, I have an athletic build, and all my wool trousers are pleated. Flat fronts are only comfortable for me in very full-cut chinos...and they've got to be FULL cut (like Bill's M1).

Just keep in mind that these magazines show what's trendy. Style is not about trend. That's not to say that flat-front trousers aren't stylish; just don't confuse the two.

What about single pleats (my preference)? Could a suit still be considered "modern" with single pleated pants?

Single pleated looks pretty modern to me, as long as the pleats face forward. Double reverse pleated trousers have a lot of fullness around the front and the lines aren't quite as clean. Nice post count.

Flat front or singel pleat for modern suits are OK in my opinion. More than one pleat are too much for modern suits.

I would say that the pleat/no pleat issue is more about line and style so as to give designers some "new" look for the season. There's almost no real play in the men's market (at least business/dress-wear) in comparison to the the women's market, where styles are easy, and acceptable, to change with each new season.

For a person of the right build, a flat front can look great. I would venture to say that for most men, a single pleat is desirable, as well as more comfortable, than a flat front. I don't believe pleats are a fashion faux paux, and I think wearing trousers which are most complimentary to your build is far better than attempting to wear the most "modern" look (although, if I could wear a flat front, I'd buy them as well).