Translate this to Arabic:(when we say "I love you", we usually say it with a capital I and a small y).

It is a tricky question, because this sentence is expressed in one word in Arabic.
I liked this question.

Nice question, عندما نقول أحبك و فإننا عادة نركز على أ المتكلم بدلاً من ك المخاطب I think this refers to the subjectivity of love in human psychology, and how before all else, we love people because they make "US" feel good and happy ! Very interesting question !

The translation of the sentence is tricky , you are asking Arabic translation of a sentence while the sentence includes references only peculiar to English language and not to Arabic .I do like this sort of quiz translations, and if I have to get the reward of trial I would translate the sentence as follows : عندما ننطق بعبارة " أنا أحبك " فأننا عادةً ما نعبر عن ذلك بتركيز على الذات مع تجاهل السبب أو مشاعر الآخر ) OR عندما نحب أحداً لا نسأل عن السبب OR الحب أعمى

Good translation .
.
What's important is that you got the meaning.
I don't think that the2nd and3rd suggestions are good.
I'd say: عندما نقول "أنا احبك" فنحن نقولها بتقديم الأنا على كاف الخطاب.