I think this page on the Developer Program Policy for impersonation might cover this.

Quoted from the page (with emphasis on the item I think those apps violate):

Impersonation

We don’t allow apps that mislead users by impersonating someone else (for example, another developer, company, entity) or another app. Don’t imply that your app is related to or authorized by someone that it isn’t. Be careful not to use app icons, descriptions, titles, or in-app elements that could mislead users about your app’s relationship to someone else or another app.
Examples of common violations

• Developers that falsely imply a relationship to another company / developer / entity / organization.

• The developer name listed for this app suggests an official relationship with Google, even though such a relationship doesn’t exist.

• Apps whose icons and titles are falsely implying a relationship with another company / developer / entity / organization.

• The app is using a national emblem and misleading users into believing it is affiliated with government.

• The app is copying the logo of a business entity to falsely suggest it is an official app of the business.

• App titles and icons that are so similar to those of existing products or services that users may be misled.

I for one am going to flag those apps because of the icon/title collisions.

What, if anything, should be done?

I think on ones who use the chameleon without permission, @donho might be able to take action against them.

I don’t know whether he can also do anything about the ones who just use the “Notepad++” name:

• https://play.google.com/store/apps/details?id=com.spectrum.mobile.inc.notepad
• https://play.google.com/store/apps/details?id=com.zoople.notable