Doing XYZ is a difficult task. This, and other questions are discussed in the following chapter.
or
Doing XYZ is a difficult task. This and other questions are discussed in the following chapter.
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Sign up to join this communityThe first sentence is wrong: you can't make it sound right with one pause in the sentence, with that pause coming after "This". If you want to use a comma after "This", you need to add a second comma after "questions":
Doing XYZ is a difficult task. This, and other questions, are discussed in the following chapter.
Your second sentence is fine.
The second sentence, the one with no commas, puts equal emphasis on "This" and on the "other questions".
The revised first sentence, the one with two commas, puts greater emphasis on "This" than on the "other questions".
This comes down to preference, or more specifically if the speaker is wanting particular emphasis on the previous sentence. If doing tasks XYZ is particularly important, especially in relation to the other chapters then include the comma.
In a normal context this sentence could do without the comma. And in a larger sense, if the sentence can do without the comma in question then don't include it.
Imagine being the listener. If someone said "This [pause] and [...]", you're going to cue in on the emphasis and its reference (xyz). Otherwise, if the other chapters and XYZ carry the same weight of importance, you wouldn't want the listener zeroing in on one over the other.