I would maybe say something about being able to write the correct crit for the correct writer.

For example, by reading a piece you can mostly guess if the writer is very new - and thus very sensitive - or has been writing for a while - and thus probably has tougher skin. With newer or at the very least younger writers you always want to make sure that you don't load them down with negative crits. You want to boost their confidence while helping them fix maybe one or two things at a time. After all, what's the rush for them to fix it all at once? Being a very positive, uplifting critique-er is important when new writers are taking those first few steps.

However, with those that have been writing and getting crits for a while, you can be a bit more blunt with what you say. I never condone mean crits, there's never any reason to be harsh or angry simply because the author made some mistakes that YOU find simple, but you can pile on the list more without sugar coating it. Being polite is valuable, but being real is also. :)

Also, I like to make sure I know what the author is looking for. You can ask them if they want you to be more blunt or if there are only specific things they want you to comment on.

Hope you can add this information in! :)