Why are they always thinking out loud !? ... The only one talking out loud in the street ...

i know right. it's weird. sometimes i do mumble to myself or whisper, but not just full voice talking out loud

Because putting everything into thought bubbles can get tiresome? It is a way to narrate without getting into long winded narratives.

Talking to yourself in public is fine, just as long as you don't get into an argument, then, perhaps it is time to find a quiet place to finish the argument ... carry on. *snicker*

Me neither, but you can't tell that secret to others, they will think that you are going to start a physical fight if you start arguing, that is why you need to find a quiet corner to finish the argument

Just don't get yourself into compromising situations like this guy:
http://www.mangago.zone/read-manga/doushitemo_furetakunai/an/doushitemo-furetakunai-chapter-7.html/9/

Well, that's the worst part of it...unconciously mumbling. Be it a patient ("Would you PLEASE stop talking to my leg?!") or later on my colleague ("Did you know that you talk to yourself while typing?") - I was always like O.O "wut?"

Hahaha...I like to have long conversations with my cats, I look at their expressions and try to figure out what their reply might be if they could answer, then I answer for them - now I do it even when I am by myself, at work or elsewhere. People will often say "what did you say?" and I answer "just talking to the _____ - which is often a computer or a wall"

Yup, those habits are scary. Back in school they used to see me as the "funny weirdo who's talking to her bag" - I was just encouraging my books, you see. "You all fit in here before, just go in obediently NOW"