Why do mumsnet keep changing the borders on threads?

[Blossomhill]

Sometimes they are plain blue and other times they have 2 dark lines all around!
God I am on here far too much

[hunkermunker]

Think this was asked a while ago (also on here too much, BH!) - are you looking at archived threads with dark lines?

[tech]

I think the messages with dark lines are ones that were written into the archive a long time ago - you mean dark lines in the blue box that says "by...."
above each message I'm presuming. One day we'll make them all the same again, maybe.

Regards,
Tech