Is this sentence ambiguous without more context?
--Where people were concerned, his threshold of boredom was low. --

Possible interpretations:

1) When he had to get on with people，he was easily bored. [ There were typos here before the edition: ...people, she eas easily...]

2) When people were worried, they were easily bored. [Here "people were" was "one was" before the edition]

3)...?

Question

Is this sentence ambiguous without more context?
--Where people were concerned, his threshold of boredom was low. --

Possible interpretations:

1) When he had to get on with  people，he was easily bored. [ There were typos here before the edition: ...people, she eas easily...]

2) When people were worried, they were easily bored. [Here "people were" was "one was" before the edition]

3)...?

Answer

#1 makes the most sense as an interpretation.
Also I would say his threshold for boredom was low. 
OR his boredom threshold was low.

Answer

The first interpretation is the only possible, I think. In the second one you've lost "his" so it isn't the same as the original sentence. It is about people without contrasting some individual man to them.

Answer

It is clear but obviously translated from another language.  More natural is "He was easily bored when talking to people."

Answer

No, the sentence is clear.  In (1) "she eas" does not make sense.  Partially because you change gender from he to she and partially as "eas" is an error, it could be "is", it could be "ease" or it could be "as".  (2) "one" is a sort of generic pronoun and sentence 2 needs some context to help the understanding.