This sort of rampant, unschooled time travel creates paradoxes that destroy the universe. To avoid this, the universe slots the whole mess into a pocket dimension and lets it collapse there, allowing the prime universe to continue on without difficulty. An example of this was most recently seen in the dramatised biography of the Doctor, in which his companion, Rose, accidently caused such a paradox and locked herself in a collapsing sub-dimension.
What does this mean? Anyone who's time travelled in this thread is dead after spending a few hours of abject terror being pursued by monsters from the time vortex. What we have left are alternate versions created to keep the prime universe's continuity intact.
Basically, everyone here is all talk and no action, coz as soon as that changes, they're reaper-fodder.
Nyah.
- Joel Fagin