I constantly travel to countries that require a visa for U.S. citizens. My U.S. passport has nary a one. I have never been asked on my return why my passport has no visas or stamps for those countries, even though I list them on my customs form. Basically, they won't have a reaction.

Immigration will not ordinarily care -- the exception sometimes being when a country has a prohibition on dual citizenship and is trying to enforce that provision on entry/exit or the country has some kinds of compliance requirements of its nationals (e.g., military service or tax-related requirement) applicable to its own nationals.

[Security contractors retained by some airlines might ask questions as they like to flip through the passports and look for stamps, but even with that there should be no problem.]

I have both New Zealand and U.S. citizenship. I keep a copy of the following regarding dual citizenship with my travel docs in case there are any questions -

http://www.travel.state.gov/travel/c.../cis_1753.html

This page from the embassy of USA in London is also of interest: admittedly it's from an embassy, and an embassy in one particular country, rather than from the Department of State, but there might be analogous pages on other embassy sights. In any case, it could be useful if someone found himself or herself subjected to questioning.

From the link above:

It doesn't mention the Supreme Court ruling, but I think it is referring to Vance v Terrazas in 1980.

Neither does it touch upon how since then the US has continued to strip naturalized US citizens of US citizenship even when the person had no intent to relinquish US citizenship.

That may be, and it might not be very helpful in the setting described if it did. :p

You mean if the OP looks like a regular British or a regular (real) Canadian. These days yiu can never tell by looks. ;)

You know there is no funny business from real Canadians or real British.

A good number of stamps in my passport are hardly readable anyway from either being stamped lightly or when the stamp is running low on ink. If anyone where to question something like that, I would point them to one of the barely readable stamps and say "I'm pretty sure that one is it..."

I'm dual US/UK and do this all the time. But got a unique situation coming up. I'm going on a trip to Russia/Belarus in a few weeks. I already have a Russian visa in my US passport, but planned on getting a visa-on-arrival in Minsk using my British passport. Would they have problems with me not having a Russian exit stamp/visa in my UK passport? I've heard Russia-Belarus is considered domestic.

I'll echo the sentiments here. I have Canadian/Australian, and I show my Canadian passport when I'm going anywhere other than Australia so my accent matches my passport. However, the law in Australia requires me to present my Australian passport on entry and exit to Australia. I however have to show the Canadian one when I check in to the airline agent in Australia to show I have permission to return home.

My son has Canadian/Australian and British citizenship. He uses the passport appropriate for whichever country he is travelling to.

At least both of your countries speak the same language (sort of) ;)

I have gotten stares with a Spanish passport and perfect American English.... or Puerto Rican accented Spanish.

Dual Passports
 

I realize this wasn't the original question but want to add an observation in case it's helpful to someone else reading this thread. US law allows US immigration authorities to strip an immigrant of permanent residency status or citizenship for taking an action that is inconsistent with the maintenance of US citizenship. There is prior case law establishing that travel on a foreign passport can be deemed by immigration authorities to be a demonstration of actions inconsistent with intention to preserve US citizenship, resulting in immediate and irrevocable deportation of a permanent resident or naturalized citizen. My advise, therefore, is to be VERY careful about travel on two passports, particularly if one is a US immigrant.

Interesting to read this point from this page — not official, but with lots of germane links.

No you would not. You would still be a British citizen you would have just entered the country on a different passport, that would not change your legal right to remain in the country for as long as you wanted to. Although you may be asked to prove your right to abode, in which case a British passport would make the most sense.

You could theoretically ask for a "Right of Abode" stamp to be placed in your foreign passport which would eliminate the need to even have a UK passport.

That's true. If you entered the UK, say, as a Canadian citizen for a short holiday and subsequently decided to stay, you would, as a British citizen, be within your rights to do that.

Even if that had been your intention all along, you would still be entitled to stay, since you are a British citizen, although you might have lied to an immigration officer in that case, which is never a good thing to have done... But in order to be admitted to the UK as a person with the right of abode, one must present either a British citizen passport or another passport with a right of abode certificate in it.

British citizens who are also citizens of another country can have a right of abode certificate placed in their non-British passport. However (sadly) since December 2006 that is only possible for British citizens who don't have a British passport.