Account suspension can occur for a variety of reasons. Repeated complaints and flags against a user are amongst those reasons. They are not the only reasons for account suspension.
In general, it is considered poor etiquette to call out specific users in posts or comments. If you feel the moderators are not scrutinizing another user closely enough, you can flag a particular comment or post of theirs and request investigation. That is one purpose of the Other... flag.
Please bear in mind that the outcome of any user investigation is not public information, so while you may feel certain that moderators are not doing anything about a user's obvious abuse, this is not usually the case. We have a sequence of steps that we go through, including corrective actions, that are invisible to the community. The purpose of privacy is to help prevent ostracizing community members.
It is a fair question to ask about how the process works. Generally speaking, it follows this pattern:
- Moderators have their attention brought to a user. This can be via flags, chat messages, Meta posts, or incidentally during routine other work. Moderators investigate the situation.
- Moderators edit or delete problematic content, or leave a comment to encourage a change in behavior. Occasionally, we use a private chat room to discuss concerns with the user or to facilitate understanding between users in real time.
- Moderators send out routine notices for continued problematic behavior. These messages contain instructions and helpful links for the user.
- Moderators issue suspensions of increasing severity. The lengths are preset by the system -- one week, one month, one year. It is uncommon for us to issue another warning after a user has been suspended once
The actions we take depend on the situation, whether we feel it is necessary to curb escalation, and whether we are immediately present or late to the party (for instance, if something is flagged over the weekend or sleeptime). We normally discuss suspensions within the mod team prior to issuing them. Our preference is to handle situations as quietly and unobtrusively as possible so as to not disrupt the community and draw negative attention to a user. High visibility is often caused by a need to defuse a rapidly escalating problem.
Additionally, remember that moderators can and do delete comments, and they can also be auto-deleted by flagging, so what you see may not be a user self-deleting comments.