martinibuster - 5:17 pm on Apr 19, 2012 (gmt 0)

and the plugin (IMHO) is no different than any web designer putting "Designed by X" on a website he designs.

I agree, 100%. But I don't think it's a positive affirmation for plug-in links. Here is why:

The "Designed by X" link has been under attack by Google since around 2003 or 2004. Manifested by a diminution of PageRank flowing (visible in the toolbar) and by various schemes for depreciating the value of the link based on relevance between the two sites as well as the location of the link. The motivation for the depreciation of a "designed by" links is foremost one of relevance. A site about a school for autistic children has zero relevance as a topic to a web design portfolio site. Throw in the second test for whether it's editorially given and you have two valid reasons why Google depreciates "Designed by" links.

So while I agree that the plug-in links are no different than "designed-by" links, this also implies they're possibly at risk for a similar depreciation in PageRank flow.