.... However, please explain what this means to me, if the safety stop is always optional:
"The Safety Stop is recommended after all dives (air supply and other considerations allowing), and required on those to 30 meters or greater, and those coming within three pressure groups of the no decompression limit." http://elearning.padi.com/company0/tools/RDP%20InsforUseMet.pdf
The PADI Recreational Dive Planner also says that the safety stop is "required" for those dives.
Does required mean required or not? And do you ignore this if you're diving with a computer?
In this case, "required" means "strongly recommended".
If you are within NDL's, you can surface at any time without any stops using a safe rate of ascent.
When I began diving, that rate was considered to be
no faster than 60 feet per minute.
Now, that rate has been reduced to
no faster than 30 feet per minute.
This reduction in ascent rate is a good thing.
The safety stop is also a very good thing. Especially after deeper dives, and really
should be performed unless there is a very compelling reason not to.
Reasons to skip the stop would be in "emergency" situations, such as a low on air situation, or if it imperative for safety reasons to get out of the water ASAP.
It is not a
required stop unless you have incurred a deco obligation, but is a strongly recommended safety buffer for all dives, especially deeper dives.
Best wishes.