Here is an interesting post- rules-wise, not for content.
It's not the only thing I've seen of the kind, but cannot find the other example. And there'll be a question for mods with this one.
So in short:
1) Said post (barely) qualifies as fitting the thread. Yes its content is nigh zero, but I can imagine it being an appropriate response. Heck, I've made posts like that.
2) Said post contains, as a sig, a link to someplace. Several posters have links to their webcomics, or videos on youtube, or whatever. Why would whatever that sig is, be different?
3) Said poster is, at least for now, really not prolific. Unlike your typical spammer, who'll flood each forum part with posts, the poster I linked to is content to post once in a blue moon.
So my spam-sense is tingling but ... I dunno, on actual analysis, this particular poster doesn't seem harmful (unless that link is to unwanted crap). So,
Mods, advise.
EDIT: Found the other, and context is crucial to establish the MO I've illustrated:
jioan wrote:The linear guild returns...
That would have made me happy awhile ago, but since they abandoned Leaky Windstaff I don't like them anymore.
This is a message with the topic "OotS". NOT spam by any measure.
Sandis wrote:Yay! I thought they'd be coming back! But it looks like there's no chance of seeing Hylda, though.

A reply from an established poster. Nothing special to see here yet ...
Vincentcnbres wrote:I dont think they are, what with the fall after pride usually being fatal and all.
Another reply, notice that it fits the conversation. BUT: the sig is (link scrubbed) "wholesale Ralph Lauren". The account was set up within the last few days. As of this EDIT, it has 3 posts.
(Also notice, to be fair, that
Sandis links to their own blog/journal; but I've always taken that to be kosher)
The whole point of this is lost if you keep it a secret.