As noted in my previous post, while the decision process regarding the quality of arguments in the digital humanities is complicated and usually involves mainly sins of omission, the basic model of an argument being open to confirmation makes for a sensible launching point to bring DH support to bear.
It is important to understand that at the level of generality under discussion here, there is no principal bias toward formal models of argumentation. By this I mean that there is no bias toward argumentation whose rules of inference have already been formalized (such as first-order predicate calculus or decision logic or similar). However, it seems to me that the interest in the ability of others to follow our arguments implies that the rules of inference I use in my argument could at least in principle be formalized. If such a "mechanical" or "symbolic" notion of inference is admitted, then Turing has good news for us: such a process of validation of an argument is a Turing-computable function and we can bring effective digital support to bear on the problem.
On the one hand it seems clear that, within the schools of the various disciplines of the humanities, rules for what are valid and proper forms of argumentation (and what are not) have developed and are taught successfully to the new generation. (This is the direction that Thomas Kuhn's arguments about the paradigms of scientific practice are hinting toward.) On the other hand, most humanities scholars would be hard-pressed to successfully formalize their underlying rules of inference. They may even have difficulties to press the forms of argumentation of their school of thinking correctly into another formalized system of inference---such as first-order predicate logic or decision logic.
The situation appears perhaps even more difficult when faced with heuristics, by which I mean argument constructs that are rule-like but are mutually exclusive and are known to be only valid in some situations. Perhaps best-known in the humanities are the rules for cross-document textual interpretation when reconstructing an Urtext, such as lectio difficilior or lectio brevior. These heuristics come into conflict if the shorter text eliminated difficulties.
But even if we are admonished not to apply these heuristics mechanically, the fact that their weighing against each other could be taught suggests that they can be explained and in the limit applied mechanically by those wishing to understand the process of our weighing, that is our argument.