Problem Statement
Profilic Wikipedia editors are sometimes individually targeted by various abusers. Those attacks often impact the talk pages of affected individuals, which is extra annoying, as it also triggers notification. Wikipedia administrators deal with those issues by temporarily protecting the talk pages of affected editors from editing, which means that newly registered users will be unable to use the talk page for anything.
When the affected editors is a Growth mentor, this means newcomers are unable to post questions to them via Special:Homepage, as that works on top of editing their user talk page. As of now, affected mentees will see a rather-ugly error message, which is recorded in the screencast below:
The Norwegian Bokmål Wikipedia recently experienced this issue and filled T367943 to introduce a new protection level, which allows any registered users through (and as such, it does not restrict any mentees).
Solutions and Risks
The problem is a rather difficult problem to solve. While we can make Special:Homepage bypass page protection (or potentially, only semiprotection), this has two important implications: (a) the mentee will be unable to follow-up on the conversation in the regular way (by hitting Reply), as the page would still be protected and (b) vandals might direct their attention to Special:Homepage, and actively harass mentors via a page-protection-bypassing feature.
Similar risks are associated with introducing a new page protection level "only autoconfirmed or mentees", especially since anyone can change their assigned mentor via the API. Those risks might be insignificant, as exploiting requires knowing MediaWIki / GrowthExperiments reasonably well, but we should consider them during the process anyway.
Alternative solutions involve providing a more reasonable user interface to the error message, either by providing a replacement mentor (T244258) or allowing mentors to provide an alternative, unprotected, talk page (T322763).
Scope of the task
Within this task, a Product decision should be made about how should this type of issues be handled. It also serves as an umbrella tasks, collecting all of the various fixes presented over the times as subtasks. Reviewing those subtasks should provide some information about possible approaches regarding the problem.