This seems more suitable for a meta question, but in any case I'm heavily against the idea of changing the original text.
Firstly, an advanced question in ancient literature should primarily be targeted towards seasoned experts in the language, with question exposure being a secondary concern, to get the best possible answer. Many obsolete variants reveal information about the text that wouldn't have been captured using the modern variant, including alternative semantic interpretations, geographical or era-specific usage (as many variants were created during eras of fragmentation) that may greatly aid in the interpretation of the text.
Secondly, StackExchange in general heavily favours a well-researched Q&A dialogue with emphasis on brevity, so if readers on the side cannot read a piece of text due to unfamiliar characters, they should take the opportunity to conduct their own research and learn something new, not to expect others to simplify the text for them (and in the end still not being able to contribute anything meaningful).
Lastly, there is no automatic detection and conversion for archaic variants to their modern forms, so this places undue weight on the question-asker.
The only time I think it is acceptable to change the variant is if it causes display problems on many computers due to encoding. However, even then it is better to provide an image of the character or describe it using ideographic description sequences.