adaptive-fill-regexp is a variable defined in `fill.el'.
Its value is
"[ 	]*\\([-–!|#%;>*·•‣⁃◦]+[ 	]*\\)*"

Regexp to match text at start of line that constitutes indentation.
If Adaptive Fill mode is enabled, a prefix matching this pattern
on the first and second lines of a paragraph is used as the
standard indentation for the whole paragraph.

If the paragraph has just one line, the indentation is taken from that
line, but in that case `adaptive-fill-first-line-regexp' also plays
a role.

You can customize this variable.