I would like to mention that when the topic of "conversion validity" comes up in a discussion by converts, it is often from the perspective of the convert who feels disrespected by not being considered Jewish by an individual or congregation because his conversion is not considered "valid" by them. But I want to mention the situation from the other point of view: I think it is also important to respect the beliefs of Jews or Jewish groups who have more traditional or strict observances than ones own and I think it is important to understand that they are not necessarily holding a strict interpretation to denigrate or purposely to exclude a convert. I feel strongly that it is incumbent upon a convert who suspects that his conversion status matters to be honest and upfront with information, and to neither lie nor purposely withhold information he suspects would be important to the others.
As an analogy, I have had to do things for the sake of kashrut that made me feel rude or bad about hurting a friend's feelings. Although I do normally eat vegetarian food cooked at homes of friends who don't keep kosher (this is one way that I am not Orthodox in practice), I can't eat at their homes during Passover due to the additional dietary restrictions and the fact that I follow more stringencies during that holiday. Less observant friends have wanted to reciprocate our seder invitations, but I can't accept them. And one friend who came to our seder was rather hurt that I could not let her bring any food that she cooked even though she keeps a vegetarian plus fish home, so her home is automatically kosher enough to bring food to my house when it is not Pesach. She asked me why I had allowed some other friends to bring food to our seder---the answer was that those friends kept strictly kosher homes with separate cookware for Pesach.
I also once had to tell non-Jewish guests that we couldn't eat the cake they had brought when we invited them for a Shabbat dinner. We had told them beforehand to not bring food, but they had bought the cake at a nearby Jewish-style deli, not understanding that it wasn't strictly kosher. We had a meat dinner, and the cake was likely to be either dairy, or at least made on dairy equipment. I felt really bad because they had gone out of their way to buy a cake that they thought would be acceptable. (Thankfully, the bottle of wine that our guests also brought was certified kosher, so at least we could use one of their gifts at the meal.)
In all the above kashrut situations, it would have been socially easier to have violated my kashrut standards, but kashrut is very important to me and dealing with these kinds of situations is something that I feel I must do in order to be true to my own religious needs and identity. I wish I didn't have to effectively impose my religious restrictions on others, but I don't want to avoid socializing with people who are not Jewishly observant (which is precisely what some very observant Jews choose to do.)
If I ever had a guest who lied and told me that a cake was certified kosher pareve which was then served at a meat meal at my house, but turned out to be dairy, I would be upset. (Even though I wouldn't have to get rid of my plates since they are Corelle which is actually a type of glass and therefore simple washing would be fine, and I could just kasher my silverware by boiling.) I would feel that the person who lied felt that my beliefs and feelings about kashrut weren't important enough for consideration.
The analogous situation would be if a male Reform convert attends a small weekday Orthodox service in which he is one of only ten men present. If the others don't know the details of his Jewish status and count him in a minyan, they will do parts of the service that can only done in the presence of a minyan even though they would not do so if they knew the visitor was a Reform convert. So the convert is causing the others to violate religious rules that they feel are important.
This is why I feel that it is disrespectful and inconsiderate for people to willfully lie about their Jewish status if they know that it is a situation where others care about the information. I try to be upfront and honest about my Jewish status or the specifics of kashrut in my house whenever I think the information might be important even it it embarrasses me. The Jews I tell this to have usually thanked me for my transparency, so I end up feeling OK about it, and the positive outcome is that the exchange serves to build trust.