collapsible property

Collapsed block nodes make little sense when dealing with rich-text
user-generated content. Rich-text libraries need to go through all sorts of
contortions right now in performance sensitive code to get around this.
Browser's themselves do things to avoid collapsing nodes (e.g. putting magic
BRs in empty block elements). These workarounds are costly and don't always
work.

Proposal: Add a collapsible property. Defaults to "auto".
auto: the current behavior of collapsing block elements when they are empty
never: empty elements don't collapse.

p {
  collapsible: never;
}

Ojan

P.S. Apologies if this has already been discussed. I couldn't find anything
in the archives.