What does this masu symbol mean?

This text is organized using section signs.

Semiotics is the study of signs and symbols used in society and culture.

What does this at sign mean?

The Schläfli symbol is a part of geometry, used to represent the shape of polyhedra.

There are many Hachijō lizards in my garden.

Would you like a cup of oolong tea?

He said, 'That kind of thing is not good.'

Thanks for helping me.

He acted foolishly and troubled everyone.