There is another thread in the forum
about diet soda that is currently active but has just about reached the end of its useful life. It may have some helpful information in there for you.
The link you posted, however, is a decent summary of the current state of research. Almost all diet drinks have 0 calories. Without any chemical energy that can be metabolized by human cells, diet drinks will not directly
contribute to weight gain. If they do contribute to weight gain or interfere with fat loss, they do so indirectly by affecting your consumption of other foods - and on that point, there is no
controlled research showing a causal link between diet soda and total calorie consumption. There is some observational research suggesting that there may
be an indirect effect, but it is equivocal at best. Until a well-designed controlled study comes along, there won't be a definitive answer.
I can tell you from first-hand experience that when I hold calories constant, the rate of weight loss or gain for me is unchanged regardless of how much diet soda I drink, but that's still just an anecdote. Go with whatever works for you and fits your comfort level.