> accent? Structure? I have no idea

Its a combination of many things, intonation and delivery, politeness (formality, honorifics etc.) level, word choice, particle choice.

Its known as onnarashii (女らしい) speech.

Its a historical thing which is gradually falling out of use. These days you tend to only mostly find it in situations where the politeness levels are needed/expected (e.g. hospitality industry).

It can happen with a lot of languages. I'm a man who learned Russian mainly through several months of traveling rural Russia where I learned quickly to avoid men: they were mostly hopeless drunks (or drug addicts) and could go from friendly to violent in an instant. So, when I needed to ask for information or directions, I turned to the women who were around. The result is that Russians find my speech distinctly female-coded.

Could be worse. He could have ended each sentence with dattebayo.

It may be more pronounced in Japanese, but it's not like it's totally without precedent in English either.

Imagine a male, non-native English speaker learning from a group of stay-at-home moms. Deep South, Midwest, take your pick. He's gonna pick up some stuff. Men in the US aren't expected to say "Aw honey," or "Bless yer heart!"

yes, you're precieved weak/femenine and possible for lack of better word, gay/lgbt

the same goes for many langauges, but you need to learn the same japanese but different form and way its spoken. I had this issue too, luckily a few japanese women helped me OL/dates so I could steer but this is a big issue