I don't get why people don't just subscribe to the issue instead of +1. Google's issue trackers have the same issue: they support starring but people insist on doing "me too" posts.
Because subscribing does not show interest/support: the repository owner does not see how many people have subscribed to the issue. Furthermore, supporting the resolution of an issue does not mean you want to be spammed with updates to said issue.
> Google's issue trackers have the same issue: they support starring but people insist on doing "me too" posts.
Google's issue tracker has the same issue to a lower extent: while everybody can see the number of stars on an issue (which is good), starring an issue requires following it and being spammed by it (which is bad).
Then again, people are by and large idiots, even on e.g. youtrack (which has non-subscripting voting) +1 comments abound: http://blog.jetbrains.com/youtrack/2013/01/making-1-mean-wha...
Only way I see to mitigate that is assuming the tracker has orthogonal subscription and voting ruthless moderation and removal of worthless "+1" comments.
Commenting on the issue automatically subscribes you to it. You have to manually unsubscribe if you don’t want to be spammed.