I am going to make the argument here that "Twitter" might be a TM for a social site, but was also a dictionary word hundreds of years prior. There is more than one possible use for this term.
I don't see anything on the site that would be infringing on the social site.
โverb (used without object)
1. to utter a succession of small, tremulous sounds, as a bird.
2. to talk lightly and rapidly, esp. of trivial matters; chatter.
3. to titter; giggle.
4. to tremble with excitement or the like; be in a flutter.
โverb (used with object)
5. to express or utter by twittering.
โnoun
6. an act of twittering.
7. a twittering sound.
8. a state of tremulous excitement.
Origin:
1325โ75; ME twiteren (v.); akin to G zwitschern
Brad
floater said:
Have used this domain for 3 years. Had some buyer interest the other day but did not know why until very recent.
Can anyone advise why it has any value?
You don't know what the buyer's motivation is. What a buyer uses the domain for is up to them. However, your website is in no way infringing with the Twitter social site as is. IMO