This user (jowierun, also on superuser and a few places besides) is finding old questions related to document conversion and adding advertising for a document conversion product. Is this kind of promotion spam? Should they make their affiliation explicit? Should the 70-odd comments be deleted?
This is a bit of a weird one actually. I've gone through the last 10 or so posts of his and the thing is, even though he keeps plugging the same products, he is actually answering the questions.
The answers all seem to be relevant and I haven't noticed any blatant copy/pasting. And the products he keeps mentioning are all free or have free versions. I agree that it feels very spammy, but should we start flagging answers en masse that might actually be useful?
In cases like these, I think the deciding factor is, are these messages being "posted indiscriminately?"
Like any other post, I think you have to look at the content, and not the user or their intentions. Many users are here for some form of self-promotion or another. Just because this user's area of expertise happens to be his product, that does not necessarily mean his content is spam.
As long as the user's posts are on-topic, helpful, and custom-written for the question being asked, I don't see that we have cause for complaint.
To be honest, this seems more like an avid fan than a spammer (see various comments responding to specific instances mentioned). Even the linkedin.com profile you found omits any relationship to the Docmosis project you think he's spamming.
And if we can't tell the difference between an avid fan who actually addresses the questions asked and someone involved in self-promotion... leaving them be is fine by me, even if they are "spamming".
If you can find better examples of spam, however, please include a list in your question; I'm sure plenty of people will evaluate them. I'm not defending him, but I am asking you to give concrete examples.
I have no problem with the concept of people answering using products they have developed or even help pay their bills. In fact, I would encourage it – as long as those users actually respond to the questions asked and follow other conventions of the community. We want experts on the site, and many of those are people who work with these things for a living.