I think it's just to increase link count. As per the initial announcement and your suggestion, links have been removed from offending accounts. This was an automated process, so there might be false positives (unlikely as it is). All the accounts still exist, so if anyone feels unfairly treated, speak up!

No objections on my part, since they seem rather dubious. Though, an alternative to outright removing the accounts might be deleting the links from them.

The question is what they hope to accomplish by creating such accounts, because why would anyone look them up in the first place? Or do they simply want to increase their search engine ranks by creating lots of links to their sites (that is if the search algorithms still work that way)?

Yet, if they really care about their accounts they will certainly speak up.

So far, I only deleted spam account which were in active use, i.e. accounts from which obvious spam messages were posted. Does anyone have any objection to purging those inactive account which have obviously only been registered for link spamming purposes as well?

I define 'obviously' by having zero posts and no information in the profile other than a commercial website link and that link being repeated in the signature (like for examine here. Would you say the assumption that this is not an account registered in good faith is safe enough?