Why can I just use a tengwar font like a normal font?
The short answer: because it isn’t a “normal” font. It’s mapped differently (note that there are some fonts that try to duplicate more normal character mapping and this will not apply for those, though you should still be careful with them because it’s impossible for the correlation to be exact). The “k” key on your keyboard, for example, won’t give you the “k” tengwa. The long(er) answer: Take a look at the following example (I’ve made it an image since it’s unfair to expect your browser to be able to display tengwar fonts correctly).
