It's normal for SSH implementations to automatically enable workarounds for each other's bugs, using the software version strings that are exchanged at the start of the connection. Typically an SSH client will have a list of server version strings that it believes to have particular bugs, and auto-enable the appropriate set of workarounds when it sees one of those strings. (And servers will have a similar list of workarounds for client software they believe to be buggy.)
If you've found a bug in an SSH server, and you'd like us to add an auto-detected workaround for it, our policy is that the server implementor should fix it first.
If the server implementor has fixed it in the latest version, and can give us a complete description of the version strings that go with the bug, then we're happy to use those version strings as a trigger to automatically enable our workaround (assuming one is possible). We won't accept requests to auto-enable workarounds for an open-ended set of version strings, such as ‘any version of FooServer, including future ones not yet released’.
The aim of this policy is to encourage implementors to gradually converge on the actual standardised SSH protocol. If we enable people to continue violating the spec, by installing open-ended workarounds in PuTTY for bugs they're never going to fix, then we're contributing to an ecosystem in which everyone carries on having bugs and everyone else carries on having to work around them.
An exception: if an SSH server is no longer maintained at all (e.g. the company that produced it has gone out of business), and every version of it that was ever released has a bug, then that's one situation in which we may be prepared to add a workaround rule that matches all versions of that software. (The aim is to stop implementors from continuing to release software with the bug – and if they're not releasing it at all any more, then that's already done!)
We do recognise that sometimes it will be difficult to get the server maintainer to fix a bug, or even to answer support requests at all. Or it might take them a very long time to get round to doing anything about it. We're not completely unwilling to compromise: we're prepared to add manually enabled workarounds to PuTTY even for bugs that an implementation hasn't fixed yet. We just won't automatically enable the workaround unless the server maintainer has also done their part.