Consider removing the word "mainstream" to describe "user agents"

[carmacleod]

Several places in the spec say "mainstream user agents".
Each instance should be reviewed, and in most (all?) cases, the word "mainstream" should be deleted.

Note: wait until after #1315 is merged.

[cookiecrook]

I agree with the removal in #1315, since that is an RFC-2119 statement, and it provides no additional value in that requirement.

However, I'm not convinced that removing all instances of the word "mainstream" is necessary. I'm certain I wrote in a few of them to emphasize to the reader "this doesn't just mean AT." If these are considered individually and it's determined that every instance in informative prose is extraneous, I'm okay deferring to the editor's decision.

[scottaohara]

There are six mentions of "mainstream" in the 1.2 spec. Five of them used in combination with 'user agents', and one instance used to describe 'browsers'.

There are only four in the latest draft. One of the ones that was removed since 1.2 was in reference to the region role. A similar instance of "mainstream user agents" still is present with the figure role, and it is now the only role that references "mainstream user agents".

I think we could probably remove this one instance and leave the others.