...pssst... hippy, I think some people were just having a bit of a joke about 'senior' being related to grizzled old PICAXEr.
... pssst2... In addition to 'experienced' and 'veteran', "seniors" is very often used for older people. "Senior Citizen", "Senior Railcard" , "Seniors tour" (tennis) etc. etc.
The odd thing about this Forum is the actual threshold at which someone becomes "senior".
Obv it would be equally daft for some poor sop to sit around grading people like some exam board.
As it stands it's pretty meaningless but gives us all a laugh.
Other Forums have different designations and methods of attaining a Guru status.
It may be useful to some and certainly an ego-kick to others.
If it causes colly-wobbles then the answer is simple - get rid of it.
Besides, if this were the "Carry On Matron" Forum then "senior member" and "old thing" could be a euphemism for something else
My neighbour has been giving me duff advice on how to fix my mower - as far as I can recall he's always been a 'complete member'.
Cheer up all - it's a lovely day for many of us!