It would be really great if there were an option to append to logs, rather than creating a new log for every conversation.
Adium has this feature - it creates a single log for every date, and appends to that log, rather than creating multiple logs per day (e.g. a new file for every new conversation, or every time an IM window is initially opened).
I'm sure that there are some users who don't need this, but it would be a handy option.
The pidgin logs are designed to be broken up into easily manageable pieces that are logically consistent, that is grouped into 'conversation' units. These files are also designed to be easily manipulable with the standard unix file tools so that they can be made to do whatever you want them to do. So you can easily, with some scripting time, create day-long collated log files based on the per-conversation log files for an entire day.
Alternatively you could write a plugin which provides a per-day logging mechanism and tell pidgin to use that, the logging mechanisms are intentionally addable from plugins for reasons exactly like this.
It seems unfortunate that such a thing can't be an option - not a requirement, but an option.
While plugins are great and make things more useful, they are not always the answer. Firefox 1.5 required an extension to save crashed or closed sessions. Firefox 2.0 included this by default. 1.5 required an extension to put a Close button on every tab, but 2.0 has this built in.
Also, seeing as I'm not a developer, I'll still post such a thing to see if anyone else is interested in seeing it be part of the default application, or added as a plugin. Sorry.
The issue isn't plugin versus internal option, it is only barely bundled plugin versus third-party plugin, it is how vital the feature is to normal, sane, every-day usage of the product. For a web browser not to save your state (given that tabs can stay open for ages, as references) is almost criminally cavalier with the users data and a horrible lack of caring for the users comfort. The fact that pidgin log files close a little more often than you might like is neither of those things, especially since you can always go back and fix the log files to be what you want if you really care to.
Plugins are not second class citizens, they are a good way of adding options that some people want without confusing or complicating the interface for everyone else. The fact that most projects treat them as second class options is a mistake.