First of all, don't put any such formatting in the BibTeX file: that is a LaTeX-style hack, and we have designed the ConTeXt system to avoid any such need. The dataset should contain only data, and hacks should be avoided. There is some limitation to this. Say, for example that the title contains mathematical symbols. One would be hard pressed not to include dollar-sign delimiters and math syntax! Another example could be "edition={second}" and "edition={2\high{nd}}". Of course, one could introduce conversion sets (like for months), but this gets complicated. How about "edition={second, revised with corrections}"?