So if an OP doesn’t like the way the thread is going...

[Tippexy]

...they can simply get it pulled?

The problem with indiscriminate deleting is that anyone can say something absolutely heinous (racist or disablist say) and then go running to HQ whinging, have it removed, and then there’s no evidence of what they said. There was far less deletion of whole threads in the past, and certainly not just on the OP’s say-so.

I would be far happier with threads being locked (as they are on other message boards) rather than posters being able to be nasty as fuck with impunity.

Or why not delete only the OPs posts and leave the replies to stand?

I remember (When it was all fields round here...) MNHQ saying they wouldn't pull a thread just because the OP didn't like how it was going, and have posted in the past bemoaning the change in position. But gosh, some threads are just awful to read now, even when the OP is clearly BU. If I were in charge, I'd have changed my mind too.