Why did you need anchor if Yahoo Q&A is rel=nofollow? Any link from there will be ignored by Google...
No html need, they will auto make it to hyperlink, you just need write th full URL which include http://www.
I heard that even if you have a nofollow link in Yahoo Q&A, Google is still going to look at it because of the rank Yahoo QA has on internet.
I have post some link , it related with content of answer question but someone always report me !!! I don't know why ?
Please share the resource where you have seen such anchored link in Yahoo Answers but i dont think we can use anchor text link in YA.....
If you try to manipulate the site using anchor text you'll likely get in trouble and the link removed regardless