IMO, if you are regularly in contact with a business contact, you can use email instead of PM. Or you can use some other messaging platform. If you can use a VPN, it will generally increase the security of public WiFi.
As a merit source, I would not merit any alt account of mine, nor any account rumored to be an alt of mine. My personal recommendation is for everyone else to do the same.
<Slightly off topic>
I actually can't recall anyone ever making that particular accusation against Quickseller
Two yaks and a tub of jello perhaps, but not merits...
</Slightly off topic>
I have gotten nothing but complements from my being a merit source. Despite having a fairly small allocation, I do my best to contribute positively to the merit economy.
People should have the freedom to do things that are unethical. When people exercise that freedom, others will frown upon you and will think less of you.