Lack of experience, training and competence.
Oh dear. It is true that I have no formal training in the field, but you know nothing of my experience or competence and, as you go on to admit in a subsequent post, you have limited familiarity with what I have been writing here for the past 14 years, and hence are less able than others to draw conclusions about my 'competence'. I suspect that not everyone here would agree with your views about my competence.
In any event, I still don't understand why you responded to my asking Harry why he was advocating a separate means of isolation for an alarm circuit when everyone else in this thread (including yourself, fairly strongly) has spoken out against it. It seems as if you have just picked a post of mine at random to reply to you with comments about me.
This is no place for modesty on my part. I obviously have limited hands-on experience, but I am pretty confident that I have at least as good a knowledge and understanding of the relevant regulations and, more importantly, the underlying electric principles as to many/most practising electricians (and more knowledge/understanding than a fair few of them).
I don't have it in for you at all.
You could have fooled me.
Your questions make me doubt your competence to install anything, ...
I'd be interested to hear which questions give rise to such doubts. I have to say that I'm sufficiently confident about my knowledge and competence that I would be happy to get on and do everything without asking any questions (and that would avoid some of the 'flak' I sometimes have to contend with) - but it provides an additional layer of confidence about safety if I ask questions to seek views about what I'm doing (in some cases from 'pros', although most of the regular contributors to this forum are not electricians).
Badly installed wiring can very easily lead to fires.
It can indeed, but I don't install wiring 'badly'