To give another deviant a direct link to this FAQ answer, use the following code in your comment or forum post:
Can I block people from interacting with me?
Yes, any deviant can block up to a maximum of 500 people for any reason from interaction.
To block another deviant, visit the 'Personal > General' section of your Settings page and scroll down to the 'Blocked Users' section.
There, you may enter the username of each person you wish to block into the field provided, one username per line. Do not include the username status symbol.
Once a block is in place, the blocked deviant will not be able to interact with the blocker and their content in any way. The blocker will also not be able to interact in any way with the deviant they blocked.
Blocking is mutual for maximum effectiveness.
Blocked interactions include commenting on each other's personal pages and content such as profiles, deviations and journals as well as general replies to one another on any area of the site. Notes can not be sent between blocker and blocked. Personal shoutboxes (if premium member) and personal forums (if premium member) are subject to blocks as well. In addition to that, +favoriting of deviations will also be prevented, as well as attempts to add one another to one's deviantWATCH. Blocking will remove both parties from each other's deviantWATCHes as well as remove any deviation favorites between both, if applicable.
Deviants which you block (or unblock) will not receive any notification of that action, however the block will be immediately evident when they visit any of the prohibited commenting areas and will encounter errors when attempting other aforementioned interactions.
If you feel that the situation is truly serious, please notify the Help Desk, so a staff member can review the situation and take whatever action is deemed necessary. Please note that if you unblock someone to continue communicating with them, you are unable to re-add them to your block list for 48 hours.
PLEASE NOTE: Using alternative accounts to contact people who have blocked you on another account is considered harassment and can result in all your deviantART accounts being suspended or permanently banned.