I'm not sure about the history of the usage of the full stop/period in Japanese, but I think it's interesting the extent to which the exclamation and question marks have become totally ingrained in the language, despite coming from outside — and quite recently. Originally there was no need for them at all, as (as is often also the case in English) whether or not a sentence is a question is clear from the grammar only.

Capital letters are a more interesting phenomenon. It seems like many people consider their use to be overly stuffy these days... even certain CEOs of certain famous AI companies.

I like using it like this .