I don't really like any of the ticketing systems I've ever needed to use, whether they've been used as bug tracking systems, user support issue management systems, or something else. Some are not too bad. I currently rely most on debbugs and ikiwiki.
debbugs is the Debian bug tracking system. See https://www.debian.org/Bugs/ for an entry point. It's mostly mail based, with a read-only web interface. You report a bug by sending an email to submission address, and (preferably) include a few magic "pseudo-headers" at the top of your message body ot identify the package and version. There's tools to make this easier, but mostly it's just about sending an e-mail. All replies are via e-mails as well. Effectively, each bug becomes is own little dedicated mailing list.
This is important. A ticket, whether it is a bug report or a support request, is all about the discussion. "Hey I have this problem..." followed by "Have you tried..." and so forth. Anything that makes that discussion easier and faster to have is better.
It is my very strong opinion, and long experience, that the best way to have such a discussion is over e-mail. A lot of modern ticketing systems are web based. They might have an e-mail mode, perhaps read-only, but that's mostly an afterthought. It's a thing bolted onto the side of the system because people like me whinge otherwise.
I like e-mail for this for several reasons.
E-mail is push, not pull. I don't need to go look at a web page to be notified that something's happened.
E-mail requires no extra usernames and passwords to manage. I don't need to create a new account every time I encounter a new ticketing system instance.
E-mail makes it very easy to respond. I can just reply to a message. I don't need to go to a web site, log in, and find a reply button.
I already have archives of my e-mail, so referring to old messages (or finding them) is easy and quick. (Mutt, offlineimap, and notmuch is my particular set of choices. But I'm not locked to them, and you can use whatever you like, too.)
E-mail is a very rich format. Discussions are inherently threaded, and various character sets, languages, attachments, and other such things just work.
For these reasons, I strongly prefer ticketing systems in which e-mails are the primary form of discussions, and e-mail is a first class citizen. I don't mind if there's other ways to participate in the discussion, but if I have to use something else than e-mail, I tend not to be happy.
I use ikiwiki to provide a distributed, shared notebook on bugs. It's a bit cumbersome, and doesn't work well for discussions.
I think we can improve on the way debbugs works, however. I've been thinking about ticketing systems for Obnam (my backup program), since it gaining enough users that it's getting hard to keep track of discussions with just an e-mail client.
Here's what I want:
Obnam users do not need to care about there being a ticketing system. They report a problem by e-mailing the support mailing list, and they keep the list in cc when conducting the discussion. This is very similar to debbugs, with the distinction that there's no ticket numbers that must be kept in the replies.
The support staff (that's me, but hopefully others as well) have access to the ticketing system, which automatically sorts incoming messages into tickets. Tickets have sufficient metadata that it's possible to track which ones have been dealt with, or still need work, and perhaps other things. Each ticket contain a Maildir with all the e-mails belonging to that ticket.
The ticketing system is distributed. I need to be able to work on tickets offline, and to synchronise instances between different computers. Just like git. It's not enough to have an offline mode (e.g., queuing e-mails on my laptop for sending to debbugs when I'm back online).
There is a reasonably powerful search engine that can quickly find the relevant tickets, and messages, based on various criteria.
I will eventually have this. I'm not saying I'm working on this, since I don't have enough free time to do that, but there's a git repository, and some code, and it imports e-mails automatically now.
Some day there may even be a web interface.
(This has been a teaser.)