The question should not be wether a theme is in a certain repository or not, but the question should be if support can be provided by third parties for a theme.

For example if the theme prevents proper support by base64-encode the code, then I would not have any motivation to support such a crippled theme. It's not supporter, nor developer, nor user friendly.

If users do not understand about what they did wrong with installing a base64 crippled theme, they can be pointed to an FAQ entry so they can correct their mistake. I mean they are free to use viruses and such, but I as a supporter would protect myself to not be influenced by such mistakes.

So the worpdress theme repository can be a valid subset (because it's all GPL compatbile in there which includes the right to modify which most often is the case in support) but it can't be the outer fence. That won't work, because there are far more themes out there that are GPL compatible.

If I imagine how many countless GPLed themes I've passed on to customers but not have published them in the repository over the years (just because of the work), it would be a pitty if the worpdress forums won't support such a good practice of free software distribution for customers that are willing to pay for free software.

Buy more free software. Support those who are doing so.