@EdwinG @heliomass As per your request:

harmful content means

(a) intimate content communicated without consent;
(b) content that sexually victimizes a child or revic- timizes a survivor;
(c) content that induces a child to harm themselves;
(d) content used to bully a child;
(e) content that foments hatred;
(f) content that incites violence; and
(g) terrorism or violent extremism content. (contenu préjudiciable)

#C34

#c34

Duty to preserve certain harmful content
41 (1) If the operator of a regulated social media service 35 makes inaccessible to all persons in Canada content that incites violence or terrorism or violent extremism con- tent, the operator must preserve that content, and all other computer data related to it that is in the operator’s possession or control, for a period of one year beginning on the day on which the content is made inaccessible.

#c34
Obligation
27 (1) Subject to section 29, an operator must, with re- spect to every regulated social media service specified by regulations made by the Governor in Council under sub- 10 section (5) that it operates, implement adequate age-veri- fication or age-estimation measures designed to prevent
a person under the age of 16 from being able to have an account with, or be otherwise registered with, the service.

[so this is where the age 16 comes from]

#c34
On age verification:

(b) do not involve the collection or use of personal information other than for age-verification or age-estimation purposes;

(c) provide for the destruction of personal informa- tion collected for age-verification or age-estimation purposes once the verification or estimation is com- pleted;

(d) provide for the protection of personal information that is collected for age-verification or age-estimation purposes until that information is destroyed; and

#c34

22 (1) If an operator has reasonable grounds to suspect that a regulated service that they operate provides access to pornographic content, the operator must, in respect of that regulated service, implement age-verification or age-estimation measures that are adequate to mitigate the risk that children will be exposed to pornographic content on the service.

#c34
So he government may or may not exempt smaller social media services based on the lobying they make because such exeptions are at discretion of minister.

If you make a law, specify in writing the threshold for what sorvices ot covers. If you are not willing to specify it, then don,t pass the law.

And how do you calculate number of users in the fediverse, or in NNTP newsgroups?