Some may have been involved in Linux at the time and this raises unhappy memories. Some may consider his action unforgiveable. Some may have butted heads with Hans Reiser in the past and be uninterested in his words because of their personal opinion. Some may be uninterested in the poster (the 8chan founder, not a regular Linux contributor). Some may see themselves as representatives of their employer and worry any response could be a PR risk if it gets interpreted as sympathizing with a murderer, or alternatively kicking a man while he's down.