Steve "Pendragon" Mescon told PC Gamer that "the idea that one single company is taking control of the name of something that hundreds of people have contributed to is surprising," echoing earlier statements. "I believe DotA should always remain a community-owned product that modders, independent developers and game fans can continue to modify and play as often as they'd like."
The counter-filing and Riot's statements seem to be coming from some assumption that Valve is planning on releasing either a paid or non-modifiable product under the "DotA" name. No product has been officially announced by Valve at this time.
For the moment, Mescon is giving Valve "the benefit of the doubt because of their history," but remains concerned by "a single organization taking ownership of the name, the community at large would no longer be able to contribute to DotA like they have for years."
For more with Mescon, head on over to the full interview at PC Gamer.