In the process of separating harmine/harmaline, I accidently added a few ml (maybe 2 or 3) of pH 4 buffer solution instead of ammonia. Carried on with ammonia and got the precipitation done, but now Im a bit concerned about buffer contamination. I asked for an MSDS for the product but havent heard back from the supplier. It was an unbranded generic type powder. I added some ammonia to a glassful of it to see if anything precipitated, but nothing did, so Im fairly confident itll remain in solution and be washed away when I rinse my harmala freebase.

Anyone have any experience/tips about this?

This ^

If you are still skeptic about it,add a couple more a/b cycles to it. Whatever that buffer is, it is water soluble and it can be diluted. I'd also filter the extracts well and squeeze the paper filters between paper towels to remove any excess liquid.

There are many buffers. Some are even "edible" (Citrate, Phosphate)
If you get datasheet you will be able to tell if you should flush or keep.

Datasheet never came, but Ive done a few rinses, so shouldnt be much buffer left. Just panicked a bit when I looked at the MSDS's for various brands of buffer, and found that some of them contain several different chemicals, including phthalates, which I wouldnt want to ingest. Anyway, Ive learned the importance of labelling chemicals clearly. All those jam jars look the same..