This was a very enlightening read; the author makes a lot of great points. In any situation, people definitely need to be held accountable for their own thoughts and actions regardless of what is or is not visible. And, I agree that there is an emphasis in 1 Tim 2:9–10 concerning economic modesty.
That being said, it seems that those who cause others to sin still have reason for concern. Herbert rightly quotes Jesus in saying that anyone who looks at a woman lustfully has committed adultery in his heart. Jesus also says that, “things that cause people to stumble [e.g., things that lead people to sin] are bound to come, but woe to anyone through whom they come…” It’s better for them to be thrown into the ocean with a millstone necklace than to cause one of His believers to stumble (Luke 17:1–2).
And though the Greek words for “modestly” (kosmios) and “decency” (aidōs) do not necessarily have sexual connotations, the word for propriety (sōphrosynē) plausibly does. In other ancient Greek texts, it often means “moderation in sensual desires, self-control, temperance” (LSJ Lexicon).
So, addressing the author’s three points, it seems to me that, (1) regardless of how the definition of “modest” changes from context to context, (2) in Jesus’ view, there appears to be culpability for not only those who stumble, but people who cause others to stumble, (3) and the Bible plausibly does mandate that those who profess to worship God dress in both an economically modest and unprovocative manner.