This is all very much the designed behavior. Whether or not the design is ideal is, of course, up to debate.
The way we think about it, naming a card A+B creates a link between A and B. Renaming the card breaks the link. So if, in your case, if you were to rename "Linux" to "On Linux", then "An Article+Linux" would be renamed as well.
I think this makes sense as a default pattern, and it certainly needs to be possible to break these links and create new ones (this is typically what I'm doing when I rename plus cards). But I suspect that we will want to add prompts to offer other possible patterns, like the ones you mention.
Yes, however I can't figure out why but I think this will change things... somehow. The idea needs to be digested a bit.
I think it has some close relation to this: http://wagn.org/Weird_behavior_creating_a_new_Something_CardType_and_then_trying_to_control_the_default_rule_of_all_Something_cards
Essentially this elevates any +card to the status of controlling that Set's name making the react in unison. This would mean we have to add extra behavior when the user want to just rename some +part of a card making it "part" of another Set. Hmm...
Renaming... from a certain perspective is really making a card part of certain Set. If Something+Part+AnotherPart changes to Something+Part+SomeOtherPart this essentially means that card has left the AnotherPart Set and now is in the SomeOtherPart Set. The + sign is really kind of a depth modifier.
For example: Something+ExtraInfo+Description means the card's content is talking about the Description of the Extra Info of something. If we rename that card from Something+ExtraInfo+Description to Something+Description+ExtraInfo we are changing nothing about the card's membership to the three sets but rather it's position relative to a 'perceived center' which in this case is the card Something. Again from a different perspective we are moving the content available at this address thereby changing it's relationship to the 'center'... Hmm....