Position (magenta star) of NGC 3259 on the M_sph^* − M_BH and σ_sph^* − M_BH scaling relations. With the bar for M_BH/M_⊙ we demonstrate the BH mass range inferred from our multi-epoch spectroscopy, bar for M_sph^*/M_⊙ shows a 3σ range for the spheroid mass estimate. Green stars – bona-fide sample of IMBH from Chilingarian et al. (2018). Magenta triangles: giant low-surface brightness galaxies (gLSB) from Saburova et al. (2021) with bulges formed mostly via in situ processes so the stellar masses of their central spheroids do not correlate with BH masses. On this figure we also demonstrate the following datasets: Baldassare et al. (2015, 2020), Zaw et al. (2020), Barth et al. (2004), Seth et al. (2014), Ahn et al. (2017, 2018), Afanasiev et al. (2018), Peterson et al. (2005), Kormendy et al. (1997), Nguyen et al. (2017, 2018).