A user has posted an answer which is correct in respect to the question. But in the end of the answer he has posted a link which has no resemblance to the answer (could be for promoting). So what should be done in that case?
Should the answer be edited and link should be removed?
Or should it be flagged as a Spam?
There are spammers who post normal answers and include a spam link at the end, and those should not be edited out, but flagged as spam accordingly, with the users being destroyed.
Try to figure out if the user is honestly trying to contribute or just here for getting traffic.
So, this should be flagged as spam and not edited out (it's completely irrelevant):
You need to change the registry to do XYZ.
This should be edited out, telling the user to stop irrelevant promotion for their website, or flagged as spam in case of multiple occurrences (or when the user adds back the link):
You need to change the registry to do XYZ.
Try to watch the answer or flag for moderator attention so that we can keep an eye.
If the answer itself is useful, and the link does not do anything to improve the answer (for example, relevant software tools, external pages for additional information, etc.), then I would say just edit to remove the link.
Then, keep an eye on the answer for a while, and if the edit gets rolled back or the link gets added back in, then you might consider flagging as spam.
You might also want to comment to points out to the user that including unrelated links in an answer is discouraged as it can be seen as spam, even if technically it isn't.
If the answer is not useful, I would suggest treating the answer in the same way as any other non-useful answer: vote down, flag or whatever is appropriate in the particular case.
