I have always wanted to received a cover with a vertical orientation but that would be impossible if my address was in the Philippines since the Roman alphabet is written horizontally. Chinese characters can be written both vertically and horizontally, and from left to right and right to left (however, if it is written vertically, it is written only right to left; this is the ancient way of writing). One must just figure out the orientation based on what is written. Just like in any language, if a set of words are written in such a way that they make no sense, then of course you know it's just a bunch of gibberish. But, in the case of Chinese, it's just that you are not reading it the right way.
According the Wu Wei Yi, the friend who sent me this cover, the sending of mail in vertical envelopes is still a common practice in Taiwan, maybe because Taiwan wants to preserve the traditional Chinese ways of doing things (?). I also found out that, because of Taiwan's special (a.k.a. confused) diplomatic status, Taiwan's postal service (ChungHwa Post) is not a member of the UPU (since China Post took over the seat for "China") and thus some of its domestic mail practices are not in line with UPU international standards. Perhaps this practice of vertical envelopes is a child of this separation from the UPU.
I was also charmed by the Chinese writing on the cover. I am no expert on Chinese script nor calligraphy, but the penmanship on this cover is very nice in my uninformed opinion, and I appreciate it very much. It seems like the sender gave some extra effort to make the cover look nice, which is something I always appreciate.
The two stamps on the top are obviously definitives of the Taiwanese flag (and flags are one of my favorite themes) and the bottommost stamps is from a 2v set issued in 1985 to celebrate the 120th birth anniversary of Sun Yat Sen, or as he is so fondly called 國父 (guófù; founder of the Republic).