What's the preferred way to alert on a barrage of offensive posts in a subthread?

[Commie Pinko Dirtbag]

Poster A posts an offensive post. He gets replies. Poster A replies in the same tone, multiple times. Subthread gets big.

Original post gets alerted without mention to other posts, but alerter later notices there's a veritable orchard of rude crap by Poster A, hanging on the "root" post.

What's the best course of action?

- Choose a different offending post from the subthread, alert on it, make a note in the comment box for the mods to look at the entire subthread?
- Same as above, but make a second alert on the "root" post, with the same comment?
- Alert on each offending post?
- Other?

[Skinner]

1. There is no "best practice" on this.

But I guess if I had to make a suggestion I would say: Alert on the post where the ugliness starts. On the alert screen, type a note in the comments section that explains that the posts starts an ugly sub-thread with lots of other rule violations.