Would any hidden factors that govern the feasibility of publication or the success of paper submission play out when an author submit two papers at the same time to a journal?
@Judie: Why? I would think that the journal would welcome papers! Do you think perhaps that maybe the papers were so poor that you had to practice submitting with the first to learn what was required to fix the second paper?
@Faysal: I have never submitted two papers simultaneously to the same journal, (too much work!) but have done so successfully to many conferences.
I would be bold enough to say that the probability of you achieving success in submitting two papers to one journal is higher that the probability of success in submitting two papers to two different journals. This is because you are familiar with the one journal and its requirements.
Well, this would depend if the two papers are strong - and are of different focus - so you would have a different editor to look at them at the same time... so, no problem.
Ian Kennedy and Theodora Issa , what if the corresponding authors i.e. submitting authors are different for both papers, with only one mutual co-author in both?
Waqar Hussain So you are sketching a scenario where paper, A by X and Y* is submitted simultaneous with paper B by X and Z* ? No problem for the journal editor. These are 2 independent papers on two research questions. All that would happen is that the editor would notice that author X is busy. It is very common for a supervisor X to have two students Y and Z who are at the same stage, but then the author order is usually reversed: Y and X, Z and X.
Based on my experience as an editor, the papers would be considered independently unless you'd let the editor know that they are somehow linked together (e.g., one should not be published before the other).