That clause doesn't apply because we're talking about an additional restriction, not an additional permission.

But, same result, because it also says:

> If the Program as you received it, or any part of it, contains a notice stating that it is governed by this License along with a term that is a further restriction, you may remove that term.

A restriction stating "you must keep branding" can be ignored. What you can require, is attribution.

The license contains (section 7):

> [you may] supplement the terms of this License with terms: > >[...] > > b) Requiring preservation of specified reasonable legal notices or > author attributions in that material or in the Appropriate Legal > Notices displayed by works containing it; or > > c) Prohibiting misrepresentation of the origin of that material, or > requiring that modified versions of such material be marked in > reasonable ways as different from the original version; or > > d) Limiting the use for publicity purposes of names of licensors or > authors of the material; or > > e) Declining to grant rights under trademark law for use of some > trade names, trademarks, or service marks;

So the requirement of branding and attribution aren't "further restriction" (which, in this context, means a restriction that is not in the AGPLv3 license text). It's after section 7's list of allowed restrictions, which, paragraph b, contains "require preservation of [...] legal notices or [...] attributions", paragraph d is made to prevent misuse of the original author reputation, and paragraph e to prevent misuse of trademarks, so they, IMHO, are all legitimate.