Thank you for your thoughtful suggestions.
In regards to hosting, we've had some rough spots in the past due to server config problems and such, but my own experience as a forum user regarding response times has been quite good for many months now. That does not mean that there are no issues related to time of day usage, internet traffic, etc. but I've not experienced them or seen them logged as errors in the event and error logs and I'm on several times a day. If you have a problem with hangs and the like, send me a PM noting time of day and your time zone, and I can check the logs to see if anything was going on at that time.
The data storage requirements for this forum data now exceed 2 GB and this is a problem. I looked at 1 & 1 hosting, and I don't see that they offer anything approaching this nor do any other shared hosting plans that I have found. This means that at some point very, very soon, I'm going to be forced into either moving to a semi-dedicated or dedicated server at a monthly cost of 10x what I'm now paying, or start deleting old messages and inactive users.
Regarding the UI, I'm not sure why you'd want to reply to a thread rather than individual post, or what difference it makes. It is the way it is because this forum is fully threaded. I suspect that most people view this forum in a flat view, rather than a threaded view, but the threaded view is supported and that is why one replies to posts.
There are several text editors to choose from in your profile. As has been noted here, the rich text editor does not behave well in Safari, so if you want to insert rich text as opposed to plain text, Firefox or IE would be your choice.
I'm familar with PHPBB and many of the others, and have no problem with them, other than the fact that migrating the data from this forum software to another would be a very substantial amount of work frought with peril. If you doubt it, visit the PHPBB site support forums and read about the problems PHPBB users are having migrating from version 2.0 to 3.0 of the same software. We lost a bunch of messages when we migrated this software to version 2. It can be done, but it's not something I'm prepared to do lightly, especially since I don't have a tool to do this.
I appreciate your suggestions and offer of help. Please be assurred that I value both and this is by no means a rejection of your points, but rather what the state of things is here at this time. Things change.
Thanks again.
-Admin