@lanodan It's OK for # and # to use in their UI "summary" property only. Especially taking into account that Mastodon actually doesn't have Title/Subject of a "toot" but "CW" only (Content Warning) that fits into semantics of #'s "summary" better than into "name".
Above decision shouldn't influence the "name" property, one of basic properties of # vocabulary.

Regarding current usage: Pump.io uses both "name" and "summary" properties since its creation in 2013, and they live together without problems.