Currently it reads as:

/** Convinience class for safe disconnection.
 * Iterators must not be used beyond the lifetime of the list
 * they work on. A connection object can be created from a
 * slot list iterator and may safely be used to disconnect
 * the referred slot at any time (disconnect()). If the slot
 * has already been destroyed, disconnect() does nothing. empty() or
 * operator bool() can be used to test whether the connection is
 * still active. The connection can be blocked (block(), unblock()).
 *
 * This is possible because the connection object gets notified
 * when the referred slot dies (notify()).
 *
 * @ingroup signal
 */

• Convinience is a typo!
• The remainder focuses only on slot iterators and even then is not terribly clear:
  • We may want to first talk about how, separate from slot iterator lifetime issues, sigc::connections can be used to disconnect(), block(), etc. - and only after that mention how those abilities can help avoid issues with slot iterator validity.
  • It should perhaps be "Slot iterators [link to info about accumulators somewhere] must not be used beyond..." or something - currently just opening talking about "Iterators" without further qualification seems liable to confuse users.

Would it be possible to make this more general, clearer about slot iterators, etc.?