The problem with H2S is that it is both highly toxic (albeit not quite at the level of HCN but surprisingly to me, too close) and with uncommon properties such as at a threshold of exposure, a suppression of the ability to detect any smell.
The latter is particularly pernicious as one can, apparently, achieve a toxic dose while not even realizing that one is continued to be exposed to the extent of having actually received a fatal dose (reputedly, a 10 minute exposure at 50-100 ppm destroys the sense of smell and thus results in the loss of ability to sense its presence through smell).
Also, pathways of fatal ingestion also relate to a limited extent to skin contact, albeit sewer workers wearing a gas mask with extended exposure could, for example, actually fall victim to this deadly poisonous gas.
The victims with fatal doses have actually been referred to as "the walking dead" as they will, progressively sicken over a course of hours, suffering irreversible organ damage leading to death.
I agree that general knowledge and labeling on H2S is deficient, and that there is an issue, as you noted: "It had no warning that hydrogen sulfide is toxic and explosive in large quantities".
I also view this a failing relating to the quality and availability of knowledge in the field of inorganic chemistry. In the case of poisoning in a car with a battery, this knowledge base apparently extends to electrochemistry as well.
As such poisoning from H2S is, in certain locales (Japan being an exception), in my opinion, can be more likely be the result of absence of knowledge and proper labeling than intentional suicide.
Some confirming references include to quote:
Hydrogen sulfide is a highly toxic gas—second only to carbon monoxide as a cause of inhalational deaths. Its mechanism of toxicity is only partially known and no specific therapy exists for sulfide poisoning....No antidote is currently available for sulfide poisoning and treatment is largely supportive.
Per the CDC, to quote:
Hydrogen sulfide is well absorbed through the lungs; cutaneous absorption is minimal. Exposure by any route can cause systemic effects...However, although its strong odor is readily identified, olfactory fatigue occurs at high concentrations and at continuous low concentrations. For this reason, odor is not a reliable indicator of hydrogen sulfide's presence and may not provide adequate warning of hazardous concentrations...Inhalation of high concentrations of hydrogen sulfide can produce extremely rapid unconsciousness and death.