This task was created during a conversation with Jared. He wants to see pure subtasks treated differently than blockers coming from somewhere else.

I don't think defining a new type of relationship (subtasks versus blocking tasks) is particularly useful, and I'm pretty certain that upsream will not want to change the current behavior.

What I'm doing with big tasks including clear subtasks is to list then in the description with curly brackets, which also reflects whether they are open or closed.

Proposing to decline this task.

This is relevant to both design and analytics (and possibly other teams) it's kind of and either or situation. The task on having Trello like dynamic checklists OR this task, but these teams need something that solves for process steps that are smaller than a task, we treat these as todos for acceptance criteria, the mobile team is probably blocked on having one of these tasks implemented as well. 

sent while mobile

Sounds like T1141: Add Acceptance Criteria/Checklist feature to Phabricator tasks, then. Are you ok with merging?

Similar but not the same, in other systems, subtasks are actually a completely different object type than tasks, for simplicity sake though, I think these could be merged. But I'd like to hear @DarTar's take on it before we merge, as his teams also requested this.

A Trello-like checklist feature would do the job for us, I'm fine with merging, thanks for the ping.