Allow comments on all questions?

Currently comments are only available on features and tools questions, which might seem a little arbitrary. Should we allow them on all questions?

### Pros:

1. More consistent
2. Lets respondents express themselves
3. Could be a good source of feedback to improve the survey

### Cons:

1. We don't actually have a way to analyze or use the comments besides just showing them in a big list.
2. Some questions (gender, race, etc.) risk generating a lot of unproductive comments.

Thoughts?

No files, tests, or entry points are named. Start by locating how comment availability is configured for feature and tools questions, then assess the implications for the other question types described here; done requires a decided policy and an agreed implementation scope.

Written by the indexing model from the issue text.