The mobile-text endpoint was introduced in the early days of the Mobile-Content-Service for experiment purposes and haven't been used ever since. We have to formally deprecate it and remove it from RESTBase and Mobile-Content-Service.
I propose to where an announcement ASAP and aim the actual removal on March 01. According to metrics the endpoint hasn't been used over the last 3 months, but there's been a report when it was silently removed last time (T139029)