Wow, I seem to have sparked quite a bit of discussion!
A lot of the discussion is about cotton and how it's not wicking. But linen is wicking, right?
You do!
I've never worn a linen base when it really counts, up a mountain, in the winter, but I often wear a linen shirt under a sweater in cooler weather. It is so comfortable because it's so absorbent for any occasional exertions ... but not wicky, I think. It does dry a lot quicker than cotton, however, and doesn't niff. And, of course, it dries much more quickly in the summer breeze, which is perhaps where the notion it wicks well comes from.
As far as I understand it, the reason that the best wicking materials function because they are not very absorbent and have longish fibres which touch the skin and lead away to the outside (or outside layer). It is why gridded microfleeces work so well. Bit warm in themselves though.
Like you, I wear kind of mainly linen now that it is becoming so cheap ... (well, if you look in the right places). It is also possible to buy high quality linen as fabric for towels etc ... brilliant towels, I should add ... light or heavy waffle. When not buying cheap shirts in sales from Hudson Bay or Amazon, we use this place for sheets, fabric, towels, duvets and so forth.
Finest pure linen bedding, tablecloths, napkins, towels, curtains, upholstery fabrics and linen clothing for sale at online linen supplier - LinenMe, based in UK
www.linenme.com
By the way, Gap sell linen t-shirts, if you are thinking of experimenting