Great question! Thank you for bringing it up.
Links to blog posts (or other material) are great if they supplement your answer, but answers posted to this site should always be informative and complete, even if the link wasn't there.
For link-only answers light on actual content
If you see an answer that doesn't "work" without the link, either complete it (wiki-style editing) or flag it as "not an answer." Folks here will work hard to curate this collection of knowledge, so when someone finally finds this site through search, the last thing you want is someone sending them elsewhere to find that information. Links sending users elsewhere are not considered an answer in the context of this site.
On excessive self-promotion
I think you're fine here. If you're primary motivation is to help build this community and add to its content, that's what this site is about. If you just happened to write about a subject elsewhere, drawing on your prior experience is all the more helpful. "Excessive self-promotion" is really meant for that individual who trawls through posts looking for every opportunity to link to their stuff. Just keep answers complete and relevant.
For you reference, here is an excerpt notifying someone of excessive self-promotion:
Hello, I'm writing in reference to your account on Sitecore Stack Exchange.
We noticed that a substantial proportion of your posts seem to exist only to promote your product or website. Per the help center:
Be careful, because the community frowns on overt self-promotion and tends to vote it down and flag it as spam. Post good, relevant answers, and if some (but not all) happen to be about your product or website, so be it. But if a huge percentage of your posts include a mention of your product or website, you're probably here for the wrong reasons.