I've noticed flaky results with the "break" tag in Drupal content posts: sometimes the summary is broken at the break tag, sometimes not.
I'd never put a lot of effort into figuring it out.
Until today.
Set up a dev site for a client yesterday and was pleasantly surprised that the break tag split the summary from the body of the content as expected.
Today, reviewing the front page, I noticed content that was not split as expected.
After spending too much time diagnosing, I realized it was the Filtered HTML vs the Full HTML Text format setting.
Searching with that new-found knowledge, I came upon a bug report, which indicates it is a regression bug and has existed for 5 years!
I'm shocked by that, and rather disgusted frankly.
Seems the solutions, such that they are, consist of:
Granting Full HTML to all users
Apply one of the questionable patches to every update of Drupal
Have users copy & paste the desired summary from the body content each and every time they modify the body.
This is pathetic that some solution hasn't yet made it into the main branch.
Blah, I have a love-hate relationship with Drupal and it tends towards hatred lately.