Having read the above posts - and the excellent fixed income thread - my conclusion is that for most investors it is sensible to hold some bonds as part of one's PF, but not too many, particularly at the present time.
This has always been my approach, from time immemorable.
My preference is about 20% of one's PF, excluding cash deposits.
This should help to provide a degree of diversification between asset classes.
Although bonds are, in principle, simple constructs, once one gets into the detail they, like most things, can become insanely complicated.
I like keeping things simple: one of the reasons why I read and enjoy Ladybird books. My approach to most things requiring decisions is to have a simple over-arching understanding, before getting bogged down in detail. Going for a run or a cycle ride also assists decision-making in my experience.
I therefore suggest that, for most investors, the best way to have some exposure to private sector and public sector debt, is to invest in multi-asset funds such as Vanguard LifeStrategy 80/20 and Fidelity Multi-Asset Allocator Adventurous W. Acc.
These are simply examples, not recommendations.