Since サヨウナラ, when written in katakana it gives a more cool/deep nuance. How about ありがとう? Do Japanese people choose to write it in katakana if they want the nuance of the word to look cooler?
It's because I want to embroider this word on a material to express thank you. Will embroidering in katakana looks stupid?
I've heard of ありがとう being written with Kanji, i.e. 有難う. This is used either in a more formal context or when typing on a computer/cell phone. Often when words are written in Katakana, even though they are of Japanese origin, are when these words are used by someone who isn't Japanese or to make the word stand out amongst the thick of the text. Even names of Japanese origin are sometimes written in Katakana, which usually suggests that this person is someone who was not born/doesn't live in Japan (日本人じゃないです).
There is no real reason why one can't write it in Katakana.
For example, around the office on one of the group chats a co-worker and I have an ongoing gag where we split the words into Hiragana and Katakana
e.g. ありがとうゴザイマス！ ドウいたしまして！
