I encountered this comment while browsing questions on Super User:
"Remember to always be careful with the registry!": Such a notice should be added, because newbies can mess up! Also, instructions for a registry backup are useful, in case something goes wrong with the .regs. – Έρικ Κωνσταντόπουλος
The answer's timeline indicates that the answer was edited to add a warning in response to the comment.
Should we add a warning to back up the registry (like the one added to said answer) to every answer that involves editing the registry?
No, I don't think this should be enforced. There are several reasons:
"The registry" isn't some mythical beast, and any changes there are really no more dangerous than changing arbitrary (system?) files on any mainstream OS. Are we really going to add a warning to every answer? That's rather extreme.
There are many areas that have nothing to do with the system itself - e.g. programs like PuTTY will store user configs there, where it's really indistinguishable from editing (and messing up) configs in any other format.
There is the potential issue of users not knowing this and just assuming registry changes are always safe... this is one point in favour of having a warning. "System32" invokes more wariness than "HKEY_LOCAL_MACHINE", I suppose.
The conventional "backup" method people seem to use is exporting certain keys to import them again later. This is not a reliable backup, and will fail to revert many cases of damage - especially those that may cause failure to boot. The correct backup method is rather more involved (backing up the actual registry hive files, which have special ACLs and are hard to access) and is really a subcase of having a proper backup of the entire system.
As a more concrete example: the export functionality does not create a .reg that will delete/clear existing keys. This means a newly added subkey or value will not be removed by the "restore"/import...
Another example: depending on ACLs on the keys themselves, the export can fail. Worse, the import can fail after a successful export if any keys are read-only. I've had this happen. False sense of security, anyone?
Most of the critical areas are already backed up anyway! System Restore and Last Known Good Configuration takes care of most issues that may cause boot failure (or other errors, with a manual restore).
We generally do not require any specific answering style. I do not believe this is a big enough issue to be a special case.
Its much like 'backup before you do any disk resizing' or 'backup before you update'
Many of the fixes people suggest involve just enough knowledge to be dangerous to yourself. And well, we'd end up with notices everywhere. Many repairs are dangerous and the OP owes it to himself to exercise proper common sense.
Personally I feel a comment would be enough. OP saw the comment, edited as necessary and the system, worked as designed with users commenting something that needed to be commented, and the poster editing it as needed.
When we give walking directions to a grown-up person, do we include warnings to "Always look both ways before crossing the street?". No we do not, even though adults sometimes get run over due to their own carelessness. Neither should we include such nanny-warnings when imparting information about file and Registry edits.