Tempted by High-Yielding Bonds?

When you see a promotion for a bond that offers eye-watering returns you have to ask the following questions:
1 - How does the yield compare to rates of comparable issuers?
2 - Is the bond issue rated by one of the top three Rating Agencies (Moody's, Fitch, S&P)?
3 - Who is giving any Guarantee or Insurance?
4 - Is that entity rated?
5 - What is the track record of the promoter?
Experience tells that the ordinary retail investor is in no way capable of giving the right answers to these basic due diligence questions.
Investors are urged to consult a financial adviser with no connection to the issuer or promoter before even considering any investment in bonds.
While many bonds issued by seasoned companies can be sold in a recognised secondary market this could be (extremely) difficult or practically impossible with bonds issued by lesser entities.