That Bannerman piece is deeply concerning.
"Unbeknown to Katie, her son had joined the charity’s youth forum, a private online community for 12-19 year-olds who are struggling with gender issues. Parents and carers are not allowed. No proof of ID or age is required, only an email address."
The platform promotes the idea parents are part of the problem. Perhaps they are but who can ascertain that by messages on the internet? Do social work do this? No. Are they social workers or trained therapists? No.
Secret forums. No proof of age required.
No mod steps in about not posting your own phone number
A mod does step in to tell them not to draw attention to Mermaids on Discord.
DISCORD 
The police have been concerned about Discord for years. They warn parents not to let their kids near it.
And frankly I'm surprised Childine is apparently so well run, given what I've seen on there in the past. I assume the big charities, having been cheerleaders, now see the writing on the wall. I've no time for them. I will never forget how the NSCPCC treated women over the rubberwankman incident and I will never trust them. It is only the LGBA that's publicly stood up for child protection in this area.
But never mind the Charity Commission, based on Bannerman's article and the platforms children are accessing, it's the NCA who should be investigating Mermaids.