from typing import List


def interesting_lines(s: str, comment_chars: str = "") -> List[str]:
    """
    Takes a string and returns a list of non-whitespace/non-comment lines,
    with each line stripped of trailing/leading whitespace.
    """
    result = []
    for line in s.splitlines():
        line = line.strip()
        if line and line[0] not in comment_chars:
            result.append(line)
    return result