sigo1 wrote:I would like to know if it is possible to ban a user as well as his/her IP so that they wouldn't be able to register for the forum again. ? if yes how
Yes, you can ban user names and IP addresses. In the ACP's Users and Groups
tab, look under the User security
item on the left navigation bar.
Personally, I don't bother banning user names; I delete their accounts and posts. If their user name is obviously spam (like "Mr. Viagra"), I disallow the user name, too (often using wildcards to ban all names with "Viagra" in them).
Also, be careful about banning IP addresses. Some (most, probably) ISPs use dynamic IP addresses, so the loser you're banning today might be your friend tomorrow. That said, if the IP addresses are in a country you don't care about (for example, I don't care about traffic from spam havens like Russia or China), you can ban that whole IP range.
sigo1 wrote:also is it possible to delete the comment / post of a user while still keeping the thread up?
Of course -- as long as the post isn't the only one in the topic.